I'm experiencing the same problem as in this question, but none of the answers fixed my problem. (edit: Setting the web.config batch attribute works, but that's a coverup, not a solution)

The problem I'm having is with a User Control that I moved from the root directory to a subdirectory within the same Web Application project. It used to work fine before I moved it. When I moved it it started giving me the error message.

It's saying that the class name exists in two dll files in Temporary ASP.NET Files. Sure enough, when I open Reflector, it's in two dlls.

If I rename the class and ascx file, everything works fine. No usages of the original name exist within any of the files in my entire application. When I rename the file, I opened all of the dll files in Temporary ASP.NET Files with Reflector, and no references to the original class name exists.

So where's this phantom reference coming from how can I fix this?