Please refer to the parameter idPrefix in the docs.
This will solve your problem. There are some posts regarding this in this forum.

Kind Regards

colNames:['id', 'Skill', 'Description', 'Tot hours', 'Q1', 'Q2', 'Q3', 'Q4']

Using the subGridRowExpanded-function as in the example Subgrid-as-grid I create a subgrid with a similar column configuration:

colNames: ['Id','Person','State','Comment', 'Tot hours', 'Q1', 'Q2', 'Q3', 'Q4'],

Both the grid and subgrid have inline editing enabled through the ondblClickRow-event.

What happens is that when I double click on a row in the subgrid, both the current grid row and current subgrid row enter into edit mode, if both rows have the same id. The two grids are filled from two different database tables that use a simple integer as an id field. If the id number happens to coincide, both the grid row and subgrid row enter edit mode. If the id numbers differ, it works as expected.

Code below:

     $("#skillNeedGrid").jqGrid({
      url:'',
      datatype: "json",
      mtype: 'GET',
      colNames:['id', 'Skill', 'Description', 'Tot hours', 'Q1', 'Q2', 'Q3', 'Q4'],
      colModel:[
                {name:'id',index:'id', width:55, hidden:true, sortable:false, editable:false, editoptions:{readonly:true,size:10}},
                {name:'skill_id',index:'skill_id', width:200, edittype:'select', editable:true, formatter:'select', editoptions:{value:skill_select_values}},
                {name:'description',index:'description', width: 400, edittype:'text', editable:true, editoptions:{size:40, maxlength:100}},
                {name:'total_hours',index:'total_hours', width:60, edittype:'text', editable:true, editoptions:{size:20}, editrules:{number:true, minValue:0, required:true}},
                {name:'q1_hours',index:'q1_hours', width:60, edittype:'text', editable:true, editoptions:{size:20}, editrules:{number:true, minValue:0, custom:true, custom_func: checkHourSum}},
                {name:'q2_hours',index:'q2_hours', width:60, edittype:'text', editable:true, editoptions:{size:20}, editrules:{number:true, minValue:0, custom:true, custom_func: checkHourSum}},
                {name:'q3_hours',index:'q3_hours', width:60, edittype:'text', editable:true, editoptions:{size:20}, editrules:{number:true, minValue:0, custom:true, custom_func: checkHourSum}},
                {name:'q4_hours',index:'q4_hours', width:60, edittype:'text', editable:true, editoptions:{size:20}, editrules:{number:true, minValue:0, custom:true, custom_func: checkHourSum}}
           ],
      jsonReader : {
         repeatitems:false
      },
      ondblClickRow: function(id) {
        if(id && id!==lastSel){
           jQuery(this).restoreRow(lastSel);
           lastSel=id;
        }
                                             
        jQuery(this).jqGrid('editRow', id,
          {
            keys:true,
            mtype:"PUT",
            url:"./skillneed/" + id,
            aftersavefunc: function() {
              $("#skillNeedGrid").jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');  
            }
          });       
      },
      loadonce: true,
      rowNum:10,
      rowList:[10,20,30],
      pager: '#skillNeedPager',
      pginput: false,
      pgbuttons: true,
      sortname: 'name',
      viewrecords: true,
      sortorder: "asc",
      recreateForm: true,
      height: "100%",
      editurl:"./skillneed",
      serializeRowData: function(postdata) {
        delete postdata["oper"];
        return JSON.stringify(postdata);
      },
      subGrid: true,
      subGridRowExpanded: function(subgrid_id, row_id) {
        var sel_skill = $("#skillNeedGrid").jqGrid('getCell', row_id, 'skill_id');
        var people_select_values = '';

        var subgrid_table_id;
        subgrid_table_id = subgrid_id+"_t";
        jQuery("#"+subgrid_id).html("<table id='"+subgrid_table_id+"' class='scroll'></table><div id='subGridPager"+subgrid_id+"'/>");
        jQuery("#"+subgrid_table_id).jqGrid({
          url:$("#skillNeedGrid").jqGrid('getGridParam', 'url') + '/' + row_id + '/assignment',
          datatype: "json",
          colNames: ['Id','Person','State','Comment', 'Tot hours', 'Q1', 'Q2', 'Q3', 'Q4'],
          colModel: [
               {name:'id',index:'id', width:55, hidden:true, sortable:false, editable:false, editoptions:{readonly:true,size:10}},
               {name:'people_id',index:'people_id', width:200, edittype:'select', editable:true, formatter:'select', editoptions:{value:people_select_values}},
               {name:'state_id',index:'state_id', width:100, edittype:'select', editable:true, formatter:'select', editoptions:{value:state_select_values}},
               {name:'comment',index:'comment', width: 200, edittype:'text', editable:true, editoptions:{size:40, maxlength:100}},
               {name:'total_hours',index:'total_hours', width:60, edittype:'text', editable:true, editoptions:{size:20}, editrules:{number:true, minValue:0, required:true}},
               {name:'q1_hours',index:'q1_hours', width:60, edittype:'text', editable:true, editoptions:{size:20}, editrules:{number:true, minValue:0}},
               {name:'q2_hours',index:'q2_hours', width:60, edittype:'text', editable:true, editoptions:{size:20}, editrules:{number:true, minValue:0}},
               {name:'q3_hours',index:'q3_hours', width:60, edittype:'text', editable:true, editoptions:{size:20}, editrules:{number:true, minValue:0}},
               {name:'q4_hours',index:'q4_hours', width:60, edittype:'text', editable:true, editoptions:{size:20}, editrules:{number:true, minValue:0}}
          ],
          jsonReader : {
             repeatitems:false
          },
          ondblClickRow: function(id) {
            if(id && id!==sgLastSel){
               jQuery(this).restoreRow(sgLastSel);
               sgLastSel=id;
            }
            jQuery("#"+subgrid_table_id).jqGrid('editRow', id,
                {
                    keys:true,
                    mtype:"PUT",
                    url:"./peopleassignment/" + id,
                    oneditfunc: function() {
                      $('select[name="state_id"] option[value="2"]').attr('disabled', 'disabled');
                      $('select[name="state_id"] option[value="3"]').attr('disabled', 'disabled');
                    },
                    aftersavefunc: function() {
                        jQuery("#"+subgrid_table_id).jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');  
                    }
                });       
          },
          serializeRowData: function(postdata) {
            delete postdata["oper"];
            return JSON.stringify(postdata);
          },
          pager: '#subGridPager' + subgrid_id,
          height: '100%',
          rowNum:20,
          sortname: 'num',
          sortorder: "asc",
          editurl:"./peopleassignment"
        });
        jQuery("#"+subgrid_table_id).jqGrid('navGrid', '#subGridPager' + subgrid_id,
        {
            edit:true, search:false, closeAfterAdd:true, closeAfterEdit:true,
            beforeRefresh: function() {
                jQuery("#"+subgrid_table_id).jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');  
            }
        },
        {
            mtype:"PUT",
            reloadAfterSubmit:true, closeAfterEdit:true, width:700, recreateForm:true,
            onclickSubmit: function (params, postdata) {
                params.url = $(this).jqGrid('getGridParam', 'editurl') + "/" + postdata[this.id + "_id"];
            },
            afterSubmit: function(response) {
              $(this).jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');  
              $("#taskGrid").jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');
              $("#taskGrid").jqGrid('setGridParam', {selrow:sel_id});

              return [true, ''];
            },
            serializeEditData: function(postdata) {
                delete postdata["oper"];
                return JSON.stringify(postdata);
            },
            afterShowForm: function(form) {
                form.find('#people_id option[value="null"]').attr('disabled', 'disabled');
                form.find('#state_id option[value="2"]').attr('disabled', 'disabled');
                form.find('#state_id option[value="3"]').attr('disabled', 'disabled');
                form.closest('div.ui-jqdialog').center();
            }
        },
        {
            reloadAfterSubmit:true, closeAfterAdd:true, closeAfterEdit:true, width:700, recreateForm:true,
            afterSubmit: function(response) {
              $(this).jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');  
              $("#taskGrid").jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');
              $("#taskGrid").jqGrid('setGridParam', {selrow:sel_id});

              return [true, ''];
            },
            serializeEditData: function(postdata) {
              delete postdata["oper"];
              postdata["skill_need_id"] = row_id;
              if (postdata["q1_hours"] === "") delete postdata["q1_hours"];
              if (postdata["q2_hours"] === "") delete postdata["q2_hours"];
              if (postdata["q3_hours"] === "") delete postdata["q3_hours"];
              if (postdata["q4_hours"] === "") delete postdata["q4_hours"];
              return JSON.stringify(postdata);
            },
            afterShowForm: function(form) {
                form.find('#people_id option[value="null"]').attr('disabled', 'disabled');
                form.find('#people_id option[value!="null"]:first').attr('selected', 'selected');
                form.find('#state_id option[value="2"]').attr('disabled', 'disabled');
                form.find('#state_id option[value="3"]').attr('disabled', 'disabled');
                form.closest('div.ui-jqdialog').center();
            }
        },
        {   mtype:"DELETE",
            reloadAfterSubmit:true,
            afterSubmit: function(response) {
              $(this).jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');  
              $("#taskGrid").jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');
              $("#taskGrid").jqGrid('setGridParam', {selrow:sel_id});
              return [true, ''];
            },
            onclickSubmit: function (params, postdata) {
              params.url = $(this).jqGrid('getGridParam', 'editurl') + "/" + postdata;
            },
            afterShowForm: function(form) {
                form.closest('div.ui-jqdialog').center();
            }
        });

      }
    });
    $("#skillNeedGrid").jqGrid('navGrid', '#skillNeedPager',
        {
            edit:true, search:false, closeAfterAdd:true, closeAfterEdit:true,
            beforeRefresh: function() {
                $("#skillNeedGrid").jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');  
            }
        },
        {
            mtype:"PUT",
            reloadAfterSubmit:true, closeAfterEdit:true, width:700, recreateForm:true,
            onclickSubmit: function (params, postdata) {
                params.url = $(this).jqGrid('getGridParam', 'editurl') + "/" + postdata[this.id + "_id"];
            },
            afterSubmit: function(response) {
              $("#skillNeedGrid").jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');  

              return [true, ''];
            },
            serializeEditData: function(postdata) {
                delete postdata["oper"];
                return JSON.stringify(postdata);
            },
            afterShowForm: function(form) {
                form.closest('div.ui-jqdialog').center();
            }
        },
        {
            reloadAfterSubmit:true, closeAfterAdd:true, closeAfterEdit:true, width:700, recreateForm:true,
            afterSubmit: function(response) {
              $("#skillNeedGrid").jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');  

              return [true, ''];
            },
            serializeEditData: function(postdata) {
                delete postdata["oper"];
                postdata["task_id"] = sel_task;
                if (postdata["q1_hours"] === "") delete postdata["q1_hours"];
                if (postdata["q2_hours"] === "") delete postdata["q2_hours"];
                if (postdata["q3_hours"] === "") delete postdata["q3_hours"];
                if (postdata["q4_hours"] === "") delete postdata["q4_hours"];
                console.log(postdata);
                return JSON.stringify(postdata);
            },
            afterShowForm: function(form) {
                form.closest('div.ui-jqdialog').center();
            }
        },
        {   mtype:"DELETE",
            reloadAfterSubmit:true,
            afterSubmit: function(response) {
              $("#skillNeedGrid").jqGrid('setGridParam',{datatype:'json'}).trigger('reloadGrid');  
              return [true, ''];
            },
            onclickSubmit: function (params, postdata) {
                params.url = $(this).jqGrid('getGridParam', 'editurl') + "/" + postdata;
            },
            afterShowForm: function(form) {
                form.closest('div.ui-jqdialog').center();
            }
        }
    );