Same problem. Upgraded from karmic and have a shutdown problem intermittantly. When it wont shutdown via the menu it will on the power button on the computer as I have set that up in preferences. Might try the suggestion of stopping 'Oo quickstarter' and see if that helps.
Also when logging on a different user the keyboard sometimes won't work. I get round it buy unplugging and replugging the keyboard.
Just some frustrating stuff which is disapointing after the flawless performance of karmic. I wanted to get the latest LTS version so I would not have to worry about upgrades every six months. Should not rush things to meet a time table IMHO.
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