1210S Projector

I just replaced my Dell 2200MM conference room projector with a 1210S. This is a ceiling mounted porjector. It's connected to a workstation using the VGA-A input and the VGA-A monitor loop through goes back to the monitor. This is exactly how my 2200 was set up. During a presentation, the workstation display showed what the projector showed. When the projector was off, the worksation display functioned fine without changing any connections. When I shut the 1210S, I loose the workstation display. Any thoughts? My 60 minutes with an untrained Dell tech was worthless. df0403@optonline.net