Black screen with KVM

Had to do an Ubuntu reinstall after a HDD failure. I have 3 computers tied to an 8 port KVM switch. When I switch from the linux host to one of the other 2 and back to the linux host I'm greeted with a black screen. No mouse movement or keyboard inputs will bring the screen back up. Have to manually reboot to get the screen working again. Before the HDD failure it worked fine. Any suggestions to fix this would be much appreciated. TIA.

EDIT: This just keeps getting better. I thought maybe updating the Nvidia GPU drivers might help but when I enter the update command I get this message. Unable to acquire the dpkg lock. (/var/lib/dpkg/lock-frontend) Is another process using it?