I downloaded and burned the 12.04 (64bit) desktop ubuntu image to a CD and booted to it. It gave me a visible desktop, but the interface is badly broken, with ghosting when dialog boxes are moved and blocky artifacts covering all text.
I tried using the self verification tool (boot, hold down a button for menu, select "Verify CD"), which claims that the CD is fine. What can I try next?
I'm using the Intel HD 4000 integrated graphics.
Update: I just kept clicking "next" and hoping that the defaults would be acceptable. Ubuntu finished installing, and I rebooted into the fresh install. The graphics artifacts appear to still be there, but I can't quite tell because all of the UI elements except for the desktop background disappear a few seconds after logging in, and I don't know how to interact with the system. (Is there a hotkey to bring up a console?)
Update 2: I did all of the above with 12.04 32-bit, with the same results. Are there any known issues with ubuntu and Intel integrated graphics?