An error like this occurs most of the time when you are trying to redirect to a new page, while the current page is still trying to complete it's process. You can find more information about the issue right here:
http://support.microsoft.com/kb/312629/EN-US/
Your call of
Response.End()
possibly causes a threadAbortionException.
Adding few lines like these may help:
HttpContext.Current.ApplicationInstance.CompleteRequest();
Response.Redirect ("myexamplepage.aspx", false);