Hi wavelet, and welcome to the wonderful world of Typemock!
First, I would suggest moving to a recent version. 5.3 is out and there's a lot that we added, fixed and made easier over time. The AAA syntax, for example makes tests much more easier to write.
As for your question, I need more input. Does the exception happen when you're not debugging as well? Please post the entire exception message, so we can investigate better.
Static methods are not different than instance methods for Isolator. You're using it correctly, so with your help, we can solve this quickly.