There was a program loaded, which should have controller a stepper motor and accepted network connections. No sign of any life there. I've tried the "complete erase" by connecting 3v3 to the gold dot, the thing doesn't respond to the USB cable being plugged in (the PC isn't seeing it). It doesn't show up in MFDeploy or DFuse.
I think it is probably dead. I forgot to mention in the original post: I have had a Netduino, a plug-top power supply and a PC power supply all fail at the same time. Oh, and my mains RCD was tripped. I suspect the PC power supply is what went, taking everything else with it. Drat.