PageRequestManagerParserErrorException with the New ASP.Net Ajax framework

I have two simple web pages with two update panels in them. The first one calls the second one using Server.Tranfer or Server.Execute and it gives the following error message:

Sys.WebForms.PageRequestmanagerParsererrorException: The Message received from the Server could not be Parsed. Common caused for this error are when the response is modified by calls to response.Write(), response filters, HttpModules, or server trace is enabled.

Now, this never happened with the previous framework, atlas. I've tried all possible solutions I could think of, but none worked so far.

Try to take a look at the following forums for?reference.
http://forums.asp.net/thread/1467462.aspx
Wish this can help you.