ASP.NET Ajax Error: Sys.WebForms.PageRequestManagerParserErrorException

Question

My website has been giving me intermittent errors when trying to perform any Ajax activities. The message I get is

Sys.WebForms.PageRequestManagerP         


        

Answer 1

I had exactly the same error.

For me it was

Missing in the httpModules section of web.config (.Net 3.5 app)

This error seems to may be related to many various things.