I've been playing around with Server 2012 RDS and I have it working great with Windows based clients. Unfortunately, our standard thin client - the Wyse S-10 running ThinOS version 6.4 - just displays a grey screen for about a minute, then disconnects. If I upgrade a Wyse to 6.5, it works.
An S-10 with ThinOS 6.4 works just fine against Server 2008 R2 RDS.
I can't upgrade the Wyse terminals to 6.5 because it would cost $80 per (last I checked), and we have 600 of them.
Network authentication is turned off on the RDS servers. Licensing is set to per user (which seems to be required on Server 2008 R2).
Any ideas?