Web build System.Reflection.ReflectionTypeLoadException: The classes in the module cannot be loaded.

I am upgrading my request for help on this forum: http://forum.unity3d.com/threads/web-build-compiler-error.192090/ The problem is I cannot add one of my library's to the project. It is compiled with .Net3.5 and only references System and two utility libraries(which themselves only reference system and are .Net3.5 compiled). I can build for stand alone fine but switching to web breaks it. I tried 2.0 but there are so many extension methods, there was no easy way to test that. Hopefully not the answer as i will have to re-wright a lot! Any other suggestions? Went through two pages of Google results but most people were simply using the wrong .Net. I had another very similar error message that was caused by not including some of the referenced dll's in my main dll. Sure that is not the case this time. **Update:** Isolated each file until i found the one that caused the issue. I have a enum.cs file with a list of enums and at the bottom this class and extension method: public static class enumExtensions { public static string DatabaseName(this MySystem System) { switch (System) { default: return "null"; } } } Cannot figure for the life of me why that is an issue. Any suggestions?