My Dell Inspiron 1720 Laptop with 12.04 with latest updates will not shut down when commanded off.
After each upgrade it will probably turn off once, the next time it is commanded off, it will shut down to the numlock, power and bluetooth lights. Holding power switch for 5 seconds completes the turnoff. Tried the terminal command
sudo shutdown -h now with no different result.
Changing the video driver from NVIDIA accelerated graphics driver (post-release updates) (version 173-updates) to NVIDIA accelerated graphics driver (post-release updates) (version current-updates) also gave me a single command shutdown but no more.