How do I force full post-back from a button within an UpdatePanel?
I had the same problem using an ImageButton inside a WebDataGrid.
I put the Line from EvilDr inside the preRender for the webdatagrid instead. Worked great!
for (int i = 0; i < wdgMyData.Rows.Count; i++)
{
ScriptManager.GetCurrent(this).RegisterPostBackControl((ImageButton)wdgMyData.Rows[i].Items[3].FindControl("btnDownloadExcel"));
}