Visual Studio 2010 Build Fails to File Copy Error

VIsual Studio 2012 on Windows 8. I was receiving the same error message on my project. Restarting Visual Studio or cleaning the obj folder manually did not help. Finally I closed all open files (Windows -> Close All Documents) and the problem went away.

This behavior was due to a newly installed Visual Studio extension called Visual Studio Achievements (http://visualstudiogallery.msdn.microsoft.com/bc7a433b-b594-48d4-bba2-a2f24774d02f)

I noticed that the .pdb file was locked by FxCop (using Unlocker) and I think that the Achievements -extension uses it. After disabling the extension I've no longer got the error mentioned above.