I'v also this problem. I use ctrl+alt+F1 to switch to console and came back to X with alt+F7 to pass this bug. I confirm too that when selecting resolution on boot the bug do not happen.
Tested on 2 differents PC + and under virtualbox on windows -- Garbled screen during install https://launchpad.net/bugs/74875 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
