I read a book from Toms Hardware a long time ago. I remember something about gold-plated pins (memory, PCI, ISA, CPU, etc.) and the slots that are plated with a different kind of metal... It stated that there would be times when the 2 different metals would build up some sort of substance and prevent proper electrical connection causing whatever the card was to fail. It would fail until the card was moved to break that build up causing the proper connection.