Next time you take the back off, you might like to try removing the BIOS battery for a few minutes & then replacing. (Usual warnings about earthing yerself & so on)
Ok, you'll lose your date-time & stuff, but there is a chance that something has been corrupted in BIOS and a reset could help.
And of course it's always poss that the memory chips have been disturbed. How about (if it's 2 or more chips) swapping them round: this will reseat them in the process... yes, one or more *could* have failed just at the time you started playing, but that would be an unfortunate coincidence.