mstest - Visual Studio 2010 locks up when running unit tests -

We are running the MSTEST Unit Test in VS2010 and whenever I do VS IDE, we are locked and '(no answer) goes. I

'If I try to click anywhere on this.

Test runs fine on other open computers with the same OS (Win 7) and VS-2010 version, is anyone run before this?

Update: should be mentioned, I can debug tests, even do not run without debugging