This is not a problem with episerver however it occurs on an episerver site.
When I do a postback on one of our templates I get this error
"Failed to load viewstate. The control tree into which viewstate is being loaded must match the control tree that was used to save viewstate during the previous request. For example, when adding controls dynamically, the controls added during a post-back must match the type and position of the controls added during the initial request."
The strange thing is that I only get the error on our production server (2008 x64). I never get it on my local machine (win7) or on our test server (2003 x86). I'm at a complete loss so I'd thought I'd check with you guys.