If you ever caught the infamous error:
Server Error in '/ws' Application. Could not load file or assembly 'App_Web_6sedkqth, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.
And application pool recycling, site restart or even the good old iisreset won't fix it, then it might be a problem with ASP.NET temporary files.
The solution is stopping IIS (alternatively, you can just stop a specific application pool):
Deleting all the files (or part of them, if just stopped a specific application pool) from the following directory:
C:\Windows\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET FilesAnd restart IIS:
Note: this is basically a repost from my previous blog.