I installed Mountain Lion at MacBook Pro. After that, the Microsoft Remote Desktop client (for Mac) does not function anymore...
AppleCare says: go to Microsoft
Microsoft says: go to Apple
I didn't realize that it wouldn't work until after I installed 10.8 either.
I have found that CoRD (cord.sourceforge.net) works well enough. I'm able to log into my XP machine from my macbook pro
Works fine here.