To be honest with you, it sounds like a bug in VS2010. For some reason it isn’t closing the open handles when the debugger stops. Killing the VS process automatically closes those handles, allowing you to access the file again. As a work around, you might look at unlocker it’s free and works exceptionally well. I know that’s not a great answer, but it should be faster than restarting VS. You might to consider sending a bug report too…
Unlocker doesn’t work on 64-bit OS, LockHunter does though.