Ahh dust... Likely a contributing factor in your troubles. Were it me, I would suggest taking the system apart and using a couple of cans of air on everything. Reseating the chips would also be helpful. Also make sure the RTC battery isn't showing the green fuzz of death. Clean all the board contacts with alcohol. Reassemble and see what happens. Since it worked once, a little cleanup and reseating should do the trick.
