Just updated from 12.10. Ubuntu cannot shutdown properly, it hangs at the purple ubuntu loading screen with dots animation still moving. It hanged about half an hour. I hold the power button to shut it down.
I happened on every boot. Please help. This is all that I know.
1/5/2013 - 6:59
sudo service lightdm restart code, and returns in console (black screen):
Asking for cache data failed Assuming drive cache: write through
then after a half screen of attempts, the screen black out (screen saving).
I pressed the power button and another shutdown procedure began.