1. If you use Visual studio to publish your site, during the publishing stage on framework 2.0 uncheck the “allow this precompiled site to be updatable”.
2. Ensure ASP.Net is installed correctly, I found that my Web Server root was configured to use ASP.Net 1.1 by default so ran the following line to fix it to 2.0 even though my site was configured for 2.0 at site level, eliminating this glitch seems logical.
C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\aspnet_regiis -i
This will also fix any mapping/installation problems.
Also ran aspnet_regiis -r
This will replace all mappings recursively to 2.0 regardless.
3. Make sure page directives at the top of aspx files are correct and ‘inherits’ is pointing to your class correctly. I could not see any problems with mine, so did not explore down this path to thoroughly, but noted others saying issues with ambiguous inheritance maybe related.
4. Declare culture in your web.config, example
<globalization uiCulture=”en” culture=”en-NZ” />
OR
<globalization uiCulture=”auto” culture=”auto” />
5. Change debug=”true” to “false” in web.config and any pages which have it set (I recommend removing it entirely from pages and just using web.config)
Source: MSDN Forum