Another thing that would help me out here: If you have software version 0.4.0, you should see a "Last Shutdown Reason" readout in the Util -> About section.
I had implemented this in mid-march to help track down the shutdown issue in the field, since it's been hard for us to replicate here in the office. On the first successful boot after a failed attempt, the software will have captured flags from the power manager and put them in this screen. It would be very helpful to know what this says the next time the issue is encountered.