...doesn't work well on the Abit IX38 QuadGT.
At least the build that's on the Ubuntu 8.10 alpha 4 CD doesn't.
However memtest86+ v1.70, found on the mythbuntu 8.04 CD, appears to be much happier.
Silly me for thinking that even though it was an alpha CD, it'd at least be good for a memtest run... wasted half the day working that out!
For anyone with similar symptoms: streams of errors start part-way into test number 2. There'll be so many errors memtest will overflow or cause some other exception and crash. I even managed to get sirens at one point.
So if it all seems a bit too... dire... don't trust that memtest is telling the truth.