VSTS and VSTestHost.Exe - not on talking terms

Thought I would install some optional updates to try and resolve some issues I was having with Vista and Visual Studio 2005. It seems I continually get the VSTestHost.exe has stopped unexpectedly error when trying to run any tests within Visual Studio. It seems there are not too many instances of this around as I can't find too much beyond simple fix suggestions that haven't worked.

After some investigations, it seemed to be trying to load Microsoft.VisualStudio.QualityTools.Common.dll (as well as a few others) and not finding them. They exist in the Common7/IDE/PrivateAssemblies area and the search that VS was doing seemed to looking in the GAC. So I GAC'ed em, but things still die. A little differently, but now I get a MessageBox like the one shown below:

Just awesome.

If anyone has any suggestions I'd love to hear them.

Oh by the way, as I alluded to at the start of the post, I tried some optional updates for Vista that I thought might help. Well it didn't, made it worse actually (the general system experience that is), so I restored. Now things are really weird. Lots of settings lost, bookmarks gone, whole heaps of things. Don't trust system restore....

Update:

I uninstalled just the Team Test components, then re-installed them again and it looks to be fixed. The uninstall and re-install process took ages, and I thought it may blow away some of my installed updates like SP1, .WCF Extensions, GAT Extensions and the like, but luckily all remained intact.