When upgrading our environment to Windows Server 2012 we experienced really slow RDP functionality towards these servers.
The sessions connected fine but the update frequency were extremely slow.
If one would log off, wait 20 seconds and log on again, the sessions would work just fine most of the time. In some cases this has to be repeated to get a working session.
If the server was restarted, the slow session returned and the above had to be repeated to get the sessions working..
So.. what the heck had happened??
With Server 2012 we had decided to start out with Microsofts Security Baseline for 2012, included in the Microsoft Security Baseline, as a base to get up to speed quickly.
Without the security baseline applied RDP works just fine. With the baseline applied, the above slowness appears.
When troubleshooting, the cause of this evil was identified (behold, for those faint of heart - stop reading now):
Under Local Policies/Security Options:
Use FIPS compliant algorithms for encryption, hashing, and signing - This was set to enabled.
If this policy is disabled, the RDP sessions works just fine..
We spent quite some time troubleshooting this and I wanted to share the annoying fact that Microsofts recommended security baseline was actually the cause of this. :(
I hope this is of help to others!