I am having a problem in building my solution in VS2008. Normally, it compiles fine in the environment. Sometimes, it fails with:
/xxx_WEB/secure/CMSManagedT
Same issue on some code I inherited.
My issue was I had a file in the app_data Folder, but it had a namespace of MyControls in it. I ended up moving that file out of the app_data folder and created a new folder "my controls".