Unfortunately it's difficult to reproduce, like it happens maybe once every week or two, though it happened both yesterday and today. I can run computer for extended periods and won't happen at all, so my expectation is it could take some time to verify if problem gone. I haven't seen it in safe mode, but unless starts happening more frequenty/predictably it's hard to say if it does/could happen in safe mode. This morning I had just started browsing the internet (forums), wasn't doing anything intensive when it started.
I had thought about temps, and I will definitely check that next time it happens. Certainly under normal operation the temp is fine (27-32C range over the cores right now), I have a Xigmatek DK-S1283 CPU cooler.
I'll check for bios updates, certainly can't hurt to move to latest, and I haven't run a memtest so will do that shortly as well.
The digital camera drivers went on pretty early (hadn't happened before then), I just mentioned it as they're from 2002 model camera or something, and vista didn't like them. In theory they have been removed, though I know it doesn't always work like that.