jQuery Grid Plugin - jqGrid

I use "multiplesearch" in "jqgrid". the search options drop down does not work ok :

for each field I put different search options :

.....colModel: [
{ name: 'UserName' ,.....,searchOptions:{sopt['bw','bn']}.......
},
name:'Amount' ,......searchOptions:{sopt['eq','ne']}......

when I select a field on the multiplesearch window , the searchoptions on the dropdown list are shown ,but when I select another field , the search options not shown ok : I see the previous searchoptions and only if I press the 'reset' button and select again that field, only than I can see the correct searchoptions .