Strang monitor problem

Ok, I figure if I can find an answer to this problem it will be here. I have a Viewsonic pf790 19" monitor that I have had for a few years, a few months ago I turned on my gaming computer and the monitor was acting as if it was having trouble displaying anything but a very low resolution and when I tried to increase it, the monitor would go blank. However I can hook it up to my laptop and it displays just fine, the laptop is set to 1024x768 so that means the resolution on the external monitor would be 1024x768 as well right? Meaning there is really nothing wrong with the CRT after all.

Now when I turn it on reattached to the game PC I get the boot splash but then it goes black, however if I attach it to any other computer I have it will run at the same resolution it was running on my gamer, and that is with the same cord as it was using on the gamer.

So that should narrow it down to a problem with the PC, but I have a loaned 19" CRT on it now, set to 1024x768 and it works fine- although the borrowed monitor is not near as good as the other one- So it's apparently not a monitor problem, and it doesn't seem to be a problem with the PC so WTF? Separately they work, together they don't, yet until the monitor stopped coming up that's the only combo I have had on that computer.

I have tried everything I can think of from upgrading my GFX card drivers, trying the other monitor port on the GFX card, everything, but no joy. The card is a ATI X850XT PE.

Now I know the solution might be to buy a new LCD monitor, and I would love to do just that but times are tough and financially it's just not in the cards for the near term, however this is the best monitor I own so I would at least like to still use it until I can upgrade to a LCD.

Any suggestions on a solution would be immensely appreciated, using the other monitor makes gaming less enjoyable.