please help - i''m stuck

i have a big problem.
on my form i have 2 gris: 1 - syncfusion grid, 1 - MS.DatagridView.
each grid is bounded to a diffrent datatble.
when dbl.clicking on the ggc, i open a second form, passing it, the 2 datatables.
when the user click on the "OK" button, i try to updaete a dataview, based on one of the datatables.
while trying i get this err msg:
"specified argument was out of range of valid values"
if i'm using 2 MS.datagridview i dont get this msg, only with the syncfusion ggc.
mabey the problem is somthing with the ggc, trying to keep the current index, and now it might change?????
please help - i'm stuck.