If you have problems with your display (typically on a CRT, but also sometimes on an LCD) where you see lines flicker across the screen or occasion discoloration, you could be experiencing electrical interference. Of course, first check to make sure your connectors are plugged in tight to the back of your PC, but if they are then try this:
1. If all your monitor cable is near either an electrical outlet or a cord carrying electrical current (i.e. surge protector), reorganize the cables so this is not the case.
2. If your monitor cable is “bundled” with other cables, try removing the monitor cable from the bundle.
While this may not solve your problem, it is a good troubleshooting step to take before you go out and buy another monitor.