Every so often on our production web servers, we get the "Could not load file or assembly App_Web…" error. There's a long thread over at ASP.NET about this issue, but I thought a simple post may help others running into this problem.
I've found an quick and easy, albeit not ideal fix for this problem. There's supposedly a hotfix for this, but there are reports that this won't actually fix the error. Until a good long term fix comes around, here's a quick way to fix this problem.
Delete all temporary ASP.NET files, by removing the folders under the following directory:
C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\
Your mileage may vary (win directory differences, etc)