Does your Visual Studio 2008 SP1 crash when you open some XAML files? It started to happen to me, for some unknown reason.
What I saw was Visual Studio completely disappearing after opening a XAML file, with the devenv.exe process being unloaded. The only traces of this kind of crash were error events in the Windows Event Viewer: ".NET Runtime version 2.0.50727.3053 - Fatal Execution Engine Error (7A035E00) (80131506)".
Luckily, a fix for this issue has been published by Microsoft. It looks like everything is back in order now.
Finally, back to productivity thanks to this hotfix and the tip I published some time ago!