Customer was recently greeted by this nasty looking error when they tried to access their Windows SharePoint v3 Server. My first impression when I saw this was that it didn’t look like a ‘standard’ SharePoint or IIS error. I checked the Central Admin site and that was working as expected.
I then proceeded to check the obvious things like the services, IIS site and so on. All working as expected (since the SharePoint Central Administration site was also working).
The issue? .NET v4.0. To fix run IIS Manager on the SharePoint Server. Locate the SharePoint site (under Sites) and click on it. Then on the right select the Basic Settings hyperlink.
Here’s what the typical SharePoint site config should look like. See the Application Pool is the typical SharePoint – 80? Here’s what the problem configuration looked like:
For some reason SharePoint was using an ASP .NET v4 Application pool. How it got that way I’ll never know but all you need to do is pull down the list of Application pools and select the standard SharePoint Application pool that will typically look like:
In this case Windows SharePoint Services v3 liked .Net Framework Version 2.0 much better than .Net Framework version 4.0.