Thanks Mattthev, I was getting errors with the stock clocks at 1284/1750, so not a case of mem OC too high.

The errors have gone away after a windows update of all things. According to the update history, it included driver updates for "Intel - SYSTEM" and "Intel - Other hardware", which I'm guessing was chipset or mobo related.

Haven't looked any further into it, as I'm happy it's been running without errors for a couple of days now.