Well if you are comfortable with opening it up I would start with pulling the socketed chips out VERY CAREFEULY. Clean all the pins with good 99% isopropyl alcohol. I use an old toothbrush for this myself. Also, clean the sockets the same way. Let it all dry out and press the chips in and out a couple times. See if that helps.
You may also have a bad kickstart disk on top of something internally being buggered.
