I figured I'd give it a bit more troubleshooting before I gave up.
I'm using a 512mb Pi board with one of either 2 Sandisk Ultra cards. I've tried it with multiple USB power sources (1-2 amp), cables, and 2-3 distros (raspbian/kali/openelec) but the result is always some variation of a theme - it will boot (usually), but at some point (anywhere from 1-10 minutes) all the lights (/act/link/fdx/etc) will go out and leave only the power (PWR) LED. I tried watching the console to see what happens when this occurs, but the display immediately goes out. No events are written to the log, so it seems that this would be some sort of electrical short.
Is this common? It's a board I ordered back when the wait was 11-12 weeks from rs/allied, and naturally it shipped from across the pond so I'm not sure how I'd return it. Should I give up and buy another one for the price? If not, what's the best way to troubleshoot it? I'm not the world's best hardware person but am willing to learn if it's at least an educational experience.