It's possible that this is an X Windows configuration problem, but considering how many things have changed on your system recently there is no way to be certain. When your computer boots up does it go through the normal boot up sequence and then loop at the message you described? If so, try going to another virtual terminal by pressing the Ctrl + Alt + F1 keys at the same time. If F1 doesn't work, try F2 instead. That should get you to a login prompt. After that you should take a look at your /etc/X11/xorg.conf file. There may even be some old ones sitting there to try.
If all of this doesn't work, another option would be going into single user mode. You could also try using rescue mode, I don't remember if Gentoo has that on their install CD or not. If they don't then you can find a Live CD like Knoppix or Damn Small Linux to get in and take a look. Best of luck...
Last edited by wmakowski; 12-25-2006 at 11:30 PM.