I have the same exact issue after upgrading a server into 2008 R2. I have the data server with administrative remote desktop on, and a Hyper-V RD/VPN server. Both servers are identical in 2008 R2 version with latest patches & updates as of 9-16-12.
The administrative RD works with 2.1.1 RDC Mac Client, the remote desktop/vpn server does not work with the mac client. So it has to do with the Remote Desktop Session Server running RDP 7.1.
I have a different 2008 R2 RD/VPN server running RDP 6.1 (7.0), it works fine with the remote 2.1.1mac client, this server has not been updated with the latest patches and updates.
My only guess is, it has to do with something in RemoteFX since this is the major new feature with RDP 7.1. I would like this to be resolved soon as possible since I have several OSX notebooks that VPN/RD into the server outside the office, as of now they
are unable to connect using the Microsoft Remote Desktop client and temporary using CoRD.
Now it would be excellent if I can downgrade RDP 7.1 into 7.0, the problems will be solved until Microsoft works the bugs out with RDP 7.1.
Lets try to solve this issue together, I'm sure it hasn't been a major issue yet because many 2008 R2 servers are running RDP 6.1 (7.0).
As I said earlier, the server without remote desktop session server is working perfect. What is the trigger causing remote session blocking the 2.1.1 mac client to login?.
Add on: I also have a different 2008 R2 server I installed in June, this setup is a replica of the server installed this week. This server is running RDP 7.1 and has the same issue with the Mac client not logging on.