can you elaborate "grounding/power supply" thing what do you mean??
If you can remember if you had a weather storm or an electrical outage right before the memory went bad.
Or if you regularly replace light bulbs around your house quite often, then you might check your house's power lines and grounding. Another clue is if you get shocked near the washer machine and dryer.
An electrician can help or advise on what to do.
I'm not talking about static build up from carpet, but the real problems. You can get a tester from the hardware store that you plug into your outlets and test them for proper wiring and grounding. (however, I have no idea how the electrical stuff is done in NZ).
Edit again, and use MBM to monitor the voltage to your memory, it should stay solid and not flucuate. In MBM, you can log those readings and look for trends.