I have updated 12.04 to 12.10 . Problem black screen

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http://askubuntu.com – I have dual boot on my PC, Windows 7 and Ubuntu. After upgrading from 12.04 to 12.10, I restarted my system and get this black screen: When I press Ctrl + Alt + F7 it allows me to login! I don’t want to have to do this each time, does anyone know how to fix it? Thank you for your help. (HowTos)