Hello,
We currently experience the issue with our Citrix Farm which is Windows 2008 R2 sp1. From time to time the server just hang. People could not log on and if the people who were on, they could not log off.
I have check with Citrix and they said that check with MS to find out as when the system hung or people report they could not log on. We can not use RDP or direct console to access the server. The only thing we can do is that reboot the server.
Regards