I assume you are talking about an LC display. If so, the problem is never RAM. Instead, it is usually a bad contact between the driver circuitry and the display panel itself. This happens because the contacts are secured by pressure, not gripping or soldering as is true with most other electronics; this is a major failure point for LCDs--and one of my biggest gripes about them.

Here's what I have suggested in the past, and it reportedly has helped in more than one case: monitor repairman that I am (or once was), it sounds like bad contacts between the driver electronics and the display itself. One relatively easy test for this problem is as follows:

With the unit on, gently grasp the left and right edges of the display. Gently twist the display (no more than a few ounces of pressure) as though you are wringing out a towel. See if the display flashes, changes, etc. This may even fix the problem by "wiping" the contacts of dirt or oxidation.