Although I can't confirm your setup, I use Snow Leopard Server 10.6 with CS5 without a problem.
I was wondering if you are using snow leopard server as your OS or if you installed client. If you are using server, does it work ok as a regular computer (i.e. internet use, etc.) I am contemplating buying a Mac Mini Server because I the specs would be great for CS5 in this price range. Any feedback would be much appreciated.