[ubuntu] Starling will not complete restart (reboot) cycle

view story

http://ubuntuforums.org – I have a first generation Starling (star1) that I've just updated to 12.04. (All software is up-to-date; the System 76 drivers have been reinstalled.) The 'restart' command that is offered at shutdown causes the computer to begin its shutdown procedure, but then it just stops: the screen goes black but the power remains on. It does not reboot. Pressing the power button shuts down the computer. Pressing the power button a second time will boot the machine. 'sudo reboot' and 'sudo shutdown -r now' yield similar incomplete results. Any idea what might cause this, and how to work around it (Hardware)