As mentioned, this sounds like a video problem, but you can try to find the root cause. To root cause the issue, I would set up a VM on a Hyper-V host with the exact same configuration as the OS that the users have (I assume they all have the same OS). If possible, get a VHD with the same configuration.
Then, I would set up the Hyper-V host / VM for kernel debugging - see here: http://blogs.msdn.com/b/ntdebugging/archive/2011/12/30/configuring-a-hyper-v-vm-for-kernel-debugging.aspx (though you might need to update some of the info on that page since you didn't specify the OS). Then, try to replicate the scenario - have any of the users log in to that machine (from home), logout / disconnect and then try to login from the Hyper-V console. If nothing happens, it's most likely a hardware / driver problem (not sure how you can debug those). If you do hit a kernel / user break, most likely a service such as
termsrv is at fault and you can take it up with Microsoft from there.
If it is a hardware problem, try to see if your video card manufacturer has some newer/beta drivers for your OS/hardware configuration.