There should be some rules in jqGrid editrules for edit row.

Which are not there now. Such as:

Maximum length validation

Minimum length validation

Phonenumber validation

alpha validation

alpha-numeric validation

Select box field required validation(may be if value is 0 reject)

zip validation

Number of  Precision validation

I have already added this in my jgrid rules in my jqGrid library.

If you permit I can commit this to jqGrid

I would suggest one more thing for jqGrid there should be provision for adding more than one custom validation.