If you get the following error: “Remote desktop connection cannot verify the identity of the computer that you want to connect to. try reconnecting to the windows-based computer or contatct your administrator.” when trying to connect OS X to a Windows Machine via RDP then do the following:

1) Delete all files in /user/{username}/Documents/RDC Connections

2) Don’t fill in the domain text box for some reason when using the Mac client if the domain text box is filled then the Windows machine at the other end can’t authenticate the connection. Seems to be worse with Vista, but I have read of this happening with 2003 also.

HTH