I can now say that, when the corruption occurs, as soon as I press Enter, I am thrown back to the login screen (and then the bug is gone).
I have disabled the automatic login in Ubuntu (btw, changing account settings crashes Gnome Shell: panel and window decorations disappear, and it no longer responds to keystrokes like CTRL-ALT-DELETE), because I figure that if I have to go to the login screen every other time I boot, I may as well start out there. Now, when the corruption occurs and I press CTRL-ALT-F1 to F7 to cycle through the consoles, about half of the screen is cleared, but the corruption stays. I clearly remember seeing consoles displayed that way a couple distros ago: the graphics driver wouldn't properly switch to text mode, and show garbled pixel junk instead of the console. I am now almost convinced that when this bug happens, Ubuntu boots into console mode, but overlays the GUI over the console in some way. I have no way of telling what the console is saying. There has to be some message there that explains what's going on. If anybody is reading this, do you know how where Ubuntu's boot logs are? Is the log overwritten with each new boot? ** Attachment added: "This is how the screen looks when switching to the console (CTRL-ALT-F1). Photo taken after typing some random garbage to make corruption more visible." https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/899669/+attachment/2629499/+files/CTRL-ALT-F1.JPG -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/899669 Title: Screen Corruption and crash after Gnome Shell login To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/899669/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp