Believe it or not a BAD PHONE will cause exactly this problem. Plug your laptop into the serial port you have connected to the VM on the DXP and unplug the tails from your station cards on a one by one basis. Press <CR> on your keyboard each time (maybe a couple times fast) while you have a tail unplugged. If you bring up the programming banner reconnect the tail and then start lifting and replacing the station jumpers one at a time while pressing <CR> each time a jumper is off. There are probably not too many people left at Comdial who know this.