Turns out I didn't kill the servo controller after all. Far as I can tell, it was just getting confused by the ~3 volts leaking through the voltage regulator while the Gumstix/Robostix combo booted. I guess by the time the Gumstix turned on the Robostix voltage regulator, the servo controller had given up due to the brown-out. The more recent Gumstix boot loader turns on the voltage regular almost immediately, and the servo controller is happy.
The gyro/accelerometer board isn't mounted yet (hence the open space above the battery pack), and I want to move the battery cells out to the arms, and there's a big mess of wires hanging out the back, but the pile of parts looks like a robot again. It's just hanging from the test stand in those pictures, but hopefully it will stand on its own before too long.