I have had memory problems before. Quite often there is a fault in the RAM itself. Try removing all your ram modules and then try them 1 at a time (always provided that you have more than one memory stick of course) If any of the RAM is faulty then your PC will show the errors you have been getting allowing you to isolate the faulty hardware. I have done this once after my PC kept giving me the BSOD and all sorts of other interesting fails it turned out one of my 4 1gig sticks was fecked.

Hope this helps