If your computer has ATI graphics, then the problem might be that you don't have the proper fglrx drivers installed.
Try booting into your installed system with the nomodeset option editing the GRUB entry by pressing "e" when selecting Ubuntu 11.10. After "quiet splash" and before the next thing to it, enter nomodeset.
That will "boot" you into ubuntu, but will actually freeze at the splash. Press Ctrl + Alt + F1 to drop into a console.
Login with your username and your password, and when you're in, type "sudo apt-get install fglrx". These are the proprietary drivers for ATI cards
Enter your password and install as required.
Reboot and Voilá
That worked for me. Might work for you if you have ATI graphics card.
ONLY if you have ATI graphics card.