I am sad to say: strange! :( I've never met similar message :(
Currently we are testing Catharsis on OS: Win xp, Win Server 2003 (both for development)
Few months ago I did test it on the Vista also and I guess it was working...
Any how try this:
1) Uninstall (if it is installed) in this order:
2) if there was some troubles - try to remove remaining rows from register. Once I had to do it also ( I was playing too much, and system started to be angry :)
3) Open VS Studion command line (e.g. Start / Programs / VS / Command line )
This will "repair the VS"
4) Install GAE
5) Install Guidance
It should work.If not, I am sorry. And if'll find the solution, please, let us know.
Enjoy Catharsis and MVC