Do you have other profilers installed? Currently Telerik JustTrace product has some conflicts with JustMock. If you had installed JustTrace I would recommend to disable it from Tool->Add-in Manager menu. Please let us know if this is your case and whether it works for you.
the Telerik team
Register for the Q2 2011 What's New Webinar Week. Mark your calendar for the week starting July 18th and book your seat for a walk through of all the exciting stuff we will ship with the new release!