Devo 7e low voltage problem

Hi - I have a Devo 7e which I managed to leave switched on overnight. This morning, I found it was down to 3.77v, bleeping at me and saying it couldn't save. It also wouldn't turn off at the power switch. I pulled out the 4xDuracell AA power pack and sure enough, each cell was showing about 1v. I put in brand new cells but when I turn the Devo on, it still shows 3.77v and after ten-fifteen seconds, the display fades away and I can't see or do anything.
I have left the Devo turned on overnight before, but that time I caught it before the voltage went down to the 3.77v and it came back fine with new batteries.
Anyone got any ideas of what is happening and how I can fix it?

Hey - the low tech approach finally solved my problem! I unplugged the power pack for twenty four hours, re-checked all of the Duracell cells and then plugged everything back in. Everything re-started just fine with 6.18v showing and the Devo working as it should.
Still odd to have the previous 3.77v showing and the power switch not turning it on or off but I'll just put that down to experience.