Today I spent few hours trying to resolve problem with our WCF server for one of our clients. Somehow everything went wrong. Our configuration is WCF server that utilize .NET 3.5, and I set it up to work under IIS6.
The errors I got were different, but in result it was all about setting permissions for IIS. Many of them were trivial, but the last one I found tricky. HTTP result code was 500, internal server error, the error in EventViewer said: Could not load file or assembly 'System.Web, Version=126.96.36.199, Culture=neutral, PublicKeyToken=xxx or one of its dependencies. Access denied.
Logically, something was wrong with access to \WINDOWS\Microsoft.NET\Framework\v188.8.131.527 folder. However, it was not so. What helped me was adding NT permissions to the folder with my WCF server to the group IIS_WPG. And this is after I tried to add permissions to user ASP_NET… and IUSR_… without success.