Comment 6 for bug 152261

Do you get this message with both the "Try Ubuntu" and "Install Ubuntu" options, specifically the latter?

If the problem still occurs can you start the desktop CD with the "Try Ubuntu" option, then edit /usr/lib/ubiquity/migration-assistant/ma-apply and write set -x on the second line, then save it and run the installer again. Please then attach /var/log/syslog from the desktop CD environment after the installer crashes.

I apologize for neglecting this bug for so long. There were several similar issues regarding the code around mounting that were fixed, but it now appears that your bug is unique from them.