Imperfect Upgrade To Ubuntu Dapper From Breezy

If, after the upgrade to Dapper, your system boots up in Dapper and comes to a blinking underline cursor and then hard locks, where CTRL+ALT+F1 won't even get you a terminal window, welcome to the club. However, perhaps I have the fix for you. It's likely how the video drivers are set up in your /etc/X11/xorg.conf file. On my system, I had Xinerama mode working with two kinds of video cards -- an Nvidia, and an ATI. Evidently from the bug reports, Xinerama is broke in Ubuntu Dapper, but, in some cases there's a fix. The fix is to take out one of the cards and leave the one that has dual-head support. Since Nvidia and Linux never get along, I yanked that bad boy. Luckily, my ATI card had the capability for dual head with an adapter I had. I put that on. Then, I rebooted and hit Esc to see the boot menu. Once there, I chose Rescue mode and logged into command line. I typed 'dpkg-reconfigure -a xserver-xorg' to automatically recreate a new xorg.conf file. Now, HERE'S THE MAGIC: edit your xorg.conf and look for your "Device" section and hunt for the "ati" card if you have one. Then, add this option in there:
Option "CRT2Position" "RightOf"
...and that's case-sensitive.
Then, reboot and when you login to the gdm and get a desktop, open the Screen Resolution control panel and choose an ultra-wide resolution that's wider than one screen. And there you go. It acts 100% like Xinerama mode.