We updated the Test Scribe Power Tool for TCM today to include a fix allowing it to function correctly in the scenario where both Visual Studio Team Suite 2008 and Visual Studio Ultimate 2010 are installed on the same machine. If you have an older version of the power tool installed already, you will need to un-install it before installing the new version. The new version of Test Scribe includes a fix that will "do the right thing" with respect for assemblies referenced from the Global Assembly Cache. You can find the landing page for Test Scribe here.