Thanks for your report. This is also bug 76976, since fixed; run 'sudo apt-get update; sudo apt-get install debconf ubiquity' in a terminal window before starting the installer to pick up the fix.
Thanks for your report. This is also bug 76976, since fixed; run 'sudo apt-get update; sudo apt-get install debconf ubiquity' in a terminal window before starting the installer to pick up the fix.