I have problem starting my Ubuntu 12.04

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http://askubuntu.com – I'm new at using linux, and i have Ubuntu 12.04 x64 and Back track 5 r3 x64. Both using the same swap partition. BT starts right all the time, but Ubuntu doesn't start right all the time. If i shut down my Ubuntu, after i start it pass through the Ubuntu loading screen and then it gets black with nothing on it. After that if i press the power button it is shutting down, and after that the same thing repeats, if i press ctrl + alt + del it restart and start normally. BT doesn't have that problem. I think it's some problem with the swap partition they share, but again I'm still a nerd at Linux. (HowTos)