I just spent some hours finding out why I could not open a RDP connection from a Windows 7 client to a W8K Server. I always had an error "Network Level Authentication not supported on client computer..." like in the old XP days without CredSSP.
I found out that migrating from another Windows 7, I copied die Default.rdp into the Douments directory. After deleting the file, everything works fine!
The entry enablecredsspsupport:i:0 caused the problem.
Just sharing, in case someone runs into the same problem.
Regards, Kilian