Ubuntu not shutting down ( going to black screen ) 12.04

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http://askubuntu.com – I am currently using a USB persistent install of ubuntu. its a simple 4GB drive with a 2.8GB partition ( casper-rw storage partition ). I setup an administrator account and set it to login automatically. I also removed ubiquity to simply use this as a go anywhere install. Heres my issue. Im logged in as my account, and I click the top right gear and select "shut down". Text pops up showing its quitting processes.. etc. and then goes to the plymouth animation. But... The screen goes black, and then it goes to the login screen. Now when im at the login screen i go into terminal ( alt+F2 ) and (HowTos)