Erratic Invalid Viewstate issue in a .NET application

Question

I seem to be getting a \"invalid viewstate\" every now and then in the event viewer for my ASP.NET application.

Most of them (95%) seem to be referencing Scrip

Answer 1

The problem seems to be the lookahead downloader in IE8.

It seems to only affect IE8 in a fairly obscure set of circumstances. One of the reasons it can go unnoticed is that a 4k chunk of data appended to a URL is often discarded by the server. One of the things that seems to make it more likely is a slow network connection. Someone in one of the below resources noted that he only had the issue with his clients in New Zealand.

Lots of people explaining two separate problems, one of which is described in the question above (malformed URLs sent to server):

http://connect.microsoft.com/VisualStudio/feedback/details/434997/invalid-webresource-axd-parameters-being-generated

Article explaining that the lookahead downloader is fixed:

http://blogs.msdn.com/b/ieinternals/archive/2010/04/01/ie8-lookahead-downloader-fixed.aspx

KB980182 – Cumulative update in which issue is fixed:

http://support.microsoft.com/kb/980182

NOTE: Because the script is automatically re-downloaded if it couldn’t be retrieved by the lookahead downloader, it should be possible to change back to the old validation mode in which .axd files were not checked for validity and remove the symptoms of the issue: