After I installed IE8 two weeks ago, I couldn't use Team Explorer anymore. I got the "Unable to cast COM object of type . . . {6D5140C1-7436 ...." error. The weird thing is it worked fine when running Visual Studio in user mode. It seems like a permission issue to me. Following the suggestion posted here by re-registering actxprxy.dll didn't fix the problem. I tried that in both system32 and syswow64 (I'm running Vista 64 SP1).
During that time I was so tied up with my work that I kind of lived with it by running 2 instances of Visual Studio; one in admin mode for my development and the other in user mode just for using Team Explorer. Until recently I needed Profiler and it crashed every time when it tried to load the report. Reinstalling Visual Studio 2008 SP1 didn't help. I had a feeling that it might be related to the initial problem so I tried re-registering actxprxy.dll again. But this time, I unregistered it first in both system32 and syswow64 before re-registering it. It worked! Both Team Explorer and Profiler are now back to live. (Visual Studio's devenv is a 32-bit process so doing so just in syswow64 should do the trick I guess).
