If recently worked with several developers that were unable to open the Team Explorer 2008 window (or if they did open it, the window was blank).  They had pre-release versions of Visual Studio 2008 installed and despite following the instructions on uninstalling previous versions, were unsucessful.  Having found the fix for this issue, I thought I'd share it in case anyone else encounters it.

Open a Visual Studio 2008 command prompt and run the following command:

devenv /setup

It will take awhile for this command to complete, but afterwards, the issue should be resolved.  Here is documentation on the /setup switch if you would like to know more about it.