upgradation issue in IE8: while upgrading 3.5 framework project to 4.0 framework

Question

After i upgraded the 3.5 framework solution to 4.0 we are facing the following issues on IE 8,

a) I have used the GridView asp:CommandField to achieve delete operation.
   So that i used the below javascript implentation on GridDataRowBound event to get
   confirmation before the row is getting deleted.

    Dim onClick As String = String.Format("if(!confirm({0})) return false;",  JsHelper.ToJs(page.Translator.Translate("Are you sure?")))
    CType(control, ImageButton).OnClientClick = onClick

    When i click Ok button it shows a blank page instead delete operation but postback is happenning and It doesn't raise the events such as
   GridViewRow_Deleting an GridViewRow_Deleted.


Looking forward for your response as earliest

--Thanks