I have recently begun working with AJAX-Enabled WCF, and have been plagued with this .NET caching issue - Could not load file or assembly App__Web__hamznvwf
Additionally to what the previous poster said, I would suggest using a tool like this to determine where the problem lies.
Wow, this one is a bit of a doozy. I did some research and apparently lots of people have been experiencing this problem for years. It's possible that you are caching types that are defined in your web site. Such types do not have an assembly, so one is randomly generated for them at runtime. The next time you recycle your web server, your types are given a different randomly generated assembly, and your cache won't be able to deserialize because the old assembly no longer exists. Here are some possible fixes you can try:
Have you tried disabling the indexing service? Also, it might be worthwhile to move to a Web application project and see if this problem persists.