One of the cool feature of the last October 08 release of TFS Power Tools has been that the members of a Team Project are shown inside Team Explorer.
One of the ideas of this is that you can use Live Messenger from inside Team Explorer to see team members status, but I and many other were seeing the error shown below as Team Explorer refreshed
There had been much talk of it being settings in the registry, UAC being used etc. but none of the fixes detailed worked for me.
However, today it has all started working after I updated to the new version of Live Messenger released in the past few days, Version 2009 (Build 14.0.8050.1202). I suspect the problem in my case was that I was using a beta version of Live Messenger