We have the same problem with RDC 2.1.1 / Any OS 10.x / Windows Server 2012 RDS Farm.
Farm properties
Security layer: RDP Security Layer
Encryption level: Client Compatible
Works fine with an Windows RDP
But getting the Remote Desktop cannot verify the identity of the computer you want to connect to using RDC 2.1.1
Even tried using the RDC client 2.1.2
Using CoRD works fine but we like to keep using MAC Remote Desktop Client (because it works fine with our 2008 RDS farm)
Any suggestions?
Thanks,