im thinking it could be faulty ram, it could be ram needing a reseed.
it could be CPU clock faults.
My 1st step (after check drivers as above) would be to re-seed your ram.
Take your Ram out, then put back in.
Even if the issue isnt with the ram, reseeding it does not hurt and can be helpful.
Also if you have a laptop, taking out the ram and or harddrive does not break most of the laptop brands warranties.
Are you getting any strange things happening with your screen, for example funny shapes on your screen, black/colourful spots, at any time while using your PC?
If so this means its the graphics card, otherwise, so far it seems unlikely.