Somewhere I have found the solution (I think it was on KubuntuForums.net). I had to boot up in Recovery Mode and select to go in command prompt mode. I had to remove the fglx package, to have he system fall back to the older graphics driver.
-- logon display screen scrambled after upgrade to 9.04 https://bugs.launchpad.net/bugs/370091 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
