Have you installed any new hardware recently. Frow what I see its a hardware or memory error. run memtest on you memory. take out any new hardware. If that does not fix it start stripping hardware out one piece at a time to determine what the culprit is.
are you overclocking?, if you have to sticks of RAM or more boot up with each one seperately and see if the error continues, this helps you locate a fualty dimm