Remote Desktop goes black while scanning with RemoteScan session hangs

We have a Windows 2008 R2 terminal server with 20 concurrent users. Intermittently, one user will go to scan from a small card reader scanner and while they are scanning on the terminal server using RemoteScan, the session will lock up to a black screen. The only way to get the session back is to kill it as an administrator. None of the other users are affected by this. The server is also a domain controller and the license server for RDP. It is a virtual server running under Hyper-V with 16GB of ram and 4 virtual cpu's. Any ideas?