Driver IRQL not less or equal - 0x000000D1

Hi, I've had around 5 random BSOD on this machine since I re-installed Windows7 yesterday. Nothing harsh, just browsing the web. I also put together an old (5 years old) Asus P4 system the other day and had exactly the same BSOD 'Driver IRQL not less or equal - 0x000000D1' I found that odd as I'd never experienced BSOD on either machine in the past! I got thinking if new windows updates had...