that also didn't Work, and postBackTrigger was still showing the same element unknown ...One of my friend redirected me to a different link
and the code is this .. worked like a charm
in page_load
Page.Form.Attributes.Add("enctype", "multipart/form-data");
ScriptManager sm = ScriptManager.GetCurrent(this);
if (sm != null)
{
sm.RegisterPostBackControl(btngvPaymentsSale);
}
also removed the trigger code ..
Working Fine now thanks