Comment 2 for bug 366529

The fix posted above did not resolve this. My system still fails to boot if FGLRX is installed under 9.04. I have to remove the driver in recovery mode in order to boot.

This isn't an isolated thing and is likely not due upgrade corruption. It specifically effects people using fglrx.

http://ubuntuforums.org/showthread.php?p=7143967#post7143967
http://ubuntuforums.org/showthread.php?t=1028284