This particular GPO has been in place since before I started managing this environment and apparently it was due to some bizarre behavior with an nVidia driver and dual monitor fat-clients. So the GPO was a simple logon script that called DisplaySwitch.exe /extend. The GPO was labelled nVidia Dual Monitor Fix and since I am not using nVidia cards in my servers I completely ignored the GPO since I assumed it was specific driver related stuff. Apparently, this was forcing the desktop image to try and extend the display to a second monitor which is fine if the zero-client had a second monitor attached but when only one monitor was connected it locked up the display until you changed the resolution. Mouse clicks were still being registered just the display wasn't refreshing.
How I figured this out was disabling inheritance on the VDI OU and logging in with nothing but the default domain policy being applied. I then attached specific GPO's necessary for our domain leaving out the nVidia GPO. I then investigated the GPO to see what it did. It definitely made me feel stupid but I'm just glad I got it figured out before these need to be deployed.
