OK, pretty certain it's an issue with the mobo right enough. BurnTest throws up an instability warning after a few runs on Maximum, advising I "lower my overclock". I'm taking that to mean that the voltage to the RAM needs boosting. They're running at stock settings, however, and are supposed to be able to do so with this mobo. 2 sticks? No problem.
This all looks correct to me, but maybe I'm missing something:
I assume, then, that I have no choice other than
- Deal with being limited to 4GB RAM, or
- Get a new mobo?