Hi,
What i understood from above is that you've enabled Paging for the gridview and wired a PageIndexChanging event and it's not firing proberly...
If my understanding is correct, then I could found a obvious mistake that the "EventArgs" being passed is wrong in the EventHandler. It should be "GridViewPageEventArgs" and not just "EventArgs" as shown below. VS will not alert you on this.
protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
}
I would recommend to use Event section of VS Properties window to create the EventHandler for you instead of coding it on your own, by double clicking on the required event, if you are not familiar with the EventArgs of a particular Event.
Hope this helps.
Thanks,
Kathir