Shaky video

My new XPS has shaky video.  I frequently get the same advice from the helpdesk, all of which I have already tried without success.  Here are the things I have already done, sorted by how often they tell me to try it again.

 

- Change the screen resolution or refresh frequency.

- Download new nVdia drivers.

- Try using a different monitor.

- Pull the video card out and put it back in.

- Enable VGA mode.

 

I have tried all these things without improvement.  To explain my problem better, the image on the screen often shakes back and forth.  Sometimes it's really obvious, sometimes it's so slight I don't notice until I get a headache 10 minutes later, and sometimes it is perfect for a few minutes, then suddenly starts shaking again.  This makes improvements particularly difficult to diagnose.  (Did that change fix it forever, or is this just one of the times it's ok, before it starts shaking a few minutes from now?)  You can often see a line of distortion roll up the screen.  Hopefully I'm explaining this well enough to understand.

 

My previous Dell computer, sitting in the same place with the same monitor, never had this problem.  This makes me think it is not some kind of interference (or it would have happened on the old computer too).  Putting a different monitor on the new computer also causes shaking, so I don't think the problem is the monitor or the location.

 

Both the monitors I tested it on were CRTs.  I guess without evidence that maybe an LCD would be better, but I'm hesitant to spend hundreds of dollars on something I don't know will help.

 

What do you recommend?  Am I the only one with this problem?