Karlos: I recently cured what I thought was a bad memory block between 60MB-64MB on a SIMM by cleaning the contacts. By magic the SIMM can be fully utilised as though there was oxidisation stopping a good contact.
I've seen a CyberVision PPC giving graphical glitches due to what the owner thinks is a dead memory chip but it's possible that it could be just a tarnished contact.
I thought the contacts on these boards were supposed to be gold, they're more like brass!