If you have installed the October 2008 TFS Power Tools (http://www.microsoft.com/downloads/details.aspx?FamilyId=FBD14EEA-781F-45A1-8C46-9F6BA2F68BF0&displaylang=en) and you are running the latest Windows Live Messenger Beta (http://download.live.com/messenger), you may come across the following error when opening Team Explorer:
Using the trusty Process Monitor to look for evidence of what the power tool is doing, we can see by filtering on devenv.exe that some calls are made to the registry to determine if MSN Messenger is “up and running”.
Looking in the registry path specified (HKCU\Software\IM Providers\MSN Messenger\UpAndRunning) and watching it whilst WLM Beta is restarted, it seems that this value is sometimes not updated by the Beta version of Windows Live Messenger and the value stays at 0. This is likely to be some sort of bug with the WLM Beta however it seems to only occur randomly. Setting the UpAndRunning value to 2 and refreshing Team Explorer resolves the issue.