Rebooting temporarily fixes it so I do not think the cable is loose. Also it affects the desktop mostly while applications don't suffer often. It seems to me like a driver/firmware issue.

If I unistall the driver, will the screen work at all before I can reinstall it?

I discovered that changing to 16-bit color depth significantly reduces the problem. I also found that it does not occur in safe mode. I have the 32 MB Mobility Radeon 9000-- I wonder if it is running out of memory and reusing memory that's already in use due to a driver problem.

Just as a test, try turning off hardware acceleration in the advanced section of the display properties. Also, try turning off "write combining" in the same section.

Reducing hardware acceleration eliminates the problem. However, I can tell a noticable difference in performance. Should I contact dell to get the video card repaired?

Have you tried setting the hardware accel. at full, and only turning off "write combining"? I read somewhere that the radeon 9000 had some problems with that setting (I could be wrong though).