So it looks like these are *really* sensitive to voltage: anything over 5V causes them to die.

Scooter has a 6V power supply, which is the likely culprit for this.

It's a problem I've had with other things, so I've started designing a power distribution board based on LM-series voltage regulators; I want to be able to support much voltages than 6V, for example 6-AA packs (9V).