This may be difficult to diagnose if you rebooted following the crash and then installed again. Could you look through http://wiki.ubuntu.com/DapperReleaseNotes/UbiquityKnownIssues and see if any of the known problems there match your situation?
-- Installer crashed https://launchpad.net/bugs/53376 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
