we got a test device in. currently no SIM in it at the moment, but i keep finding it either powered off or in the middle of a reboot. could be doing anything, and then the screen goes black. sometimes it'll come right back, other times i'm finding that i'm needing to pull the battery in order to come back up again.

i understand that this device isn't really out there yet, but i'm throwing this out in case anyone else is seeing this problem. the no SIM isn't an issue right?

Have you run the Desktop Manager > Switch Device Wizard on the device and if so did you move any apps from a 5.0 or lesser device to it? Any themes?

Many apps are compatible, not all.
Did you move a Media Card from another device to it? That could cause the rebooting also, as it did to 4.2 > 5.0 upgrades in the past, as the media card image thumbnails were not compatible with the higher OS.

If nothing else, I've linked ATT OS in the Sticky Threads above it you need to reload the OS.

Good luck.