It strikes me that you can buy 50' and even 100' shielded VGA cables.
...and as I mentioned above, you can make "VGA to Cat5" adapters (see the relevant bits from the instructable here
). I've run a video signal over a 200' patch cord using a couple of homemade adapters and it was a reasonably good signal. So long as you don't need to rout it through switching equipment this would go through wall plugs, patch panels, etc.
Actually, that's a really funny idea--I'm not actually positive how well it would work, but I suspect it would work just fine--make some HD15-to-Cat5 adapters and some USB-to-cat5 adapters (I think you could put two USB signals through one wire, but not sure of distance), and then actually use a patch panel and two Cat5 jumpers (one for video, one for keyboard/mouse) to patch your keyboard/monitor to the computer you want to control. Et voila!
Sounds pretty low-tech and cheesy, but you know I bet it would work, and no messy conversion to IP required if your cabling situation allowed it.