Comment 1 for bug 94878

This sounds like a bug that was fixed already, but can you please run the installer again using the --debug option and attach /var/log/syslog and /var/log/installer/debug to this bug report? Helpful instructions can be found here: https://wiki.ubuntu.com/DebuggingUbiquity/AttachingLogs

I'd prefer you use a daily image to test this, but if that's not possible, the one you have will suffice. The latest daily live CD can be found here:
http://cdimage.ubuntu.com/daily-live/current/

Thanks!