After developing a WPF application without Source Control, I decided to add the solution to TFS.
After doing so whenever I opened the main window.xaml file in Design
I just came across an answer that worked in my situation. Using the ngen utility to delete the native image cache fixed the problem. I don't know which image it was exactly, as I did not go through then one at a time, but it worked and I was able to keep PowerCommands!
The command is:
ngen /delete *
For a full recount of my tale I've posted it on my blog, including what I found out about ngen and the native image cache. I think I still have some more to learn about it, but it's a start.