Here's a nagging problem that has me stumped.

We had a pretty vanilla setup of two Dell Precision workstation 390's running RHEL 4. DVI monitor output from each was connected to a 2 port DVI switchbox from avocent. Their USB output was connected to the box too. This enabled 1 usb mouse and keyboard, and one monitor (connected to the monitor's vga output via a cable with DVI->VGA adapter on one end, and DVI on the other to plug into the box) to be shared by both machines.

Pretty vanilla, and was working since before I came.

While the User was away others needed the monitor and a cable so they borrowed her's. She returned days later and I was asked to hook everything back up for her. And of course - it now won't work!

When everything is reconnected as decribed above, the monitor registers no signal from either PC. If I unplug the monitor from the switchbox and hook it up directly to either one, you can see the screen and usb switching of the keyboard/mouse is seen to be fine. But we can no longer see video when the switchbox is in the mix.

NEW DVI SWITCHBOX swapped in had the same peoblem! USB switches fine. Neither machine gets video.
OLD BOX connected to two other machines works fine, allowing seemless monitor sharing.

I tried different cables. No improvement.

Shut EVERYTHING down - both computers, switchbox, monitor -then rehooked everything back up to the original state, powered on everything, still monitor shows no video when connected to switchbox (or is it properly, computers output no video to monitor when switchbox is in the mix?).

But monitor manually re-plugged - live btw - from one machine to the other works fine.

I AM STUMPED! Anyone have a suggestion? Is it time to give up and just use VNC?

-Van