Compilation Error: The type 'ASP.global_asax' exists in both DLLs

In my case the problem occurred in a virtual application's bin folder. Looking into this bin-folder you will probably see two files (an information I found here): App_global.asax.dll App_global.asax.compiled

Removing these resolves the error. The App_global.asax.dll is generated at runtime too which causes the problem. I am however still investigating how these files got there, so comments are definitely welcome!