I was trying the Windows 7 beta and could not get the Mac to connect by RDP. I kept getting..
"You were disconnected from the Windows-based computer because of problems during the licensing protocol."
Easy fix. Find a copy of RDP client for Mac 1.0 and try again. You'll need to lower the security level in the remote access pane and maybe you'll need to remove the folder /User/Shared/Microsoft/RDC Crucial Server Information.