When I run my unit tests in my project I am seeing a result \"Not executed\" for every one. I have restarted my computer so I doubt this is some kind of hung process issue.
Another reason for "Failed to queue test run 'XXX'. The path is not of a legal form." is that the account does not have a profile loaded.
E.g. when you start mstest.exe with CreateProcessAsUser() and forget to call LoadUserProfile() as well.