This sounds like a hardware problem, not software. This is the type of problem you see from a bad video card or monitor, and hardware does fail.
You need to try the monitor on another system and see how it works. You need to try a different monitor on your system and see how it works. There is no other easy way to troubleshoot this type of problem.
Monitor flickers and jumps but only when I am online --
It does not do it all the time, but often enough to make being online unpleasant. I have a 19" ViewSonic LCD. This began about a month ago after 1 1/2 years without a problem. I have checked with ViewSonic and they do not think it is the monitor. I have checked with Dell and they do not think it is the Video card. I have checked with AOL and they dunno. My settings are those recommended by ViewSonic. There have been no recent changes made to the system. I removed a desk lamp that I thought might be causing interference. I have a feeling it might be a problem with AOL -- does that make sense? Appreciate any suggestions.
Dell Dimension 8250 2.66GHz
512MB PC1066 RDRAM
64MB DDR NVIDIA GeForce4 TI 4200 Graphics w/TV-Out
80GB 7299 RPM Ultra ATA Hard Drive