When it rebooted, however, it failed with a message saying that fsck had failed and that I should repair manually and reboot. However, e2fsk showed no errors when run manually on all partitions. Irritatingly, maintainance mode also crashes (at "Searching for info file ...") when run from the DVD and I've been using the CD.
Where do I go from here? (I paid money for this .... )
CD install is 32bit only. Probably you have a not quite working mix of 32bit and 64bit rpms in your system now. I guess fsck just segfaults early because something is broken. There may be more things broken outside fsck. You could try to fix it from the rescue system, but easiest would be probably to save the data you still need on a different partition and do a full reinstall of your / -Andi