You mention adding more RAM: if nothing else works, you might want to consider looking at that as a possible source of problems.

RAM can be defective…also, some systems require specific memory configurations (E.G.: a certain combination of # of SIMM components, or only certain memory sizes in certain RAM slots). To debug *that* problem, you could start by going back to a known state (E.G.: removing the new RAM) and seeing if the problem persists. If the problem goes away, there is something wrong with the new RAM you added.

I’m doubtful that your RAM has anything to do with it, though- however, it *is* possible.