I have tried this on two different Mac Minis. The first Mac Mini was a Mid-2011 i5 with 16GB of RAM running a Windows Server 2008 R2 guest. 1 core, 8GB and 6GB of guest RAM. The second Mac Mini is a 2012 i7 quad core with 16GB RAM running Windows Server 2012 guest. Both hosts were running 10.8.2. The problem is identical on both hosts and both guests.
The issue is that at least once a day, the guest's screen will randomly freeze up. The server is actually still running because I can Remote Desktop into it just fine, but the screen will be frozen at a specific time. Clicking in the screen, pressing Control Alt Delete does nothing. The only way to unfreeze the screen is to reboot the guest OS. After reboot, I can access the console just fine. Keep in mind that during this process, the server and all of the applications are available.
I have scoured the logs, and I cannot find anything unusual. Has anybody experienced anything like this and do you have a fix for it?