Comment 2 for bug 985354

On trying to install Ubuntu 12.04 (32 bit), I encountered a very similar problem. The relevant part of syslog appears to be:

May 7 09:38:13 ubuntu install.py: Exception during installation:
May 7 09:38:13 ubuntu install.py: Traceback (most recent call last):
May 7 09:38:13 ubuntu install.py: File "/usr/share/ubiquity/install.py", line 689, in <module>
May 7 09:38:13 ubuntu install.py: install.run()
May 7 09:38:13 ubuntu install.py: File "/usr/share/ubiquity/install.py", line 129, in run
May 7 09:38:13 ubuntu install.py: self.copy_all()
May 7 09:38:13 ubuntu install.py: File "/usr/share/ubiquity/install.py", line 465, in copy_all
May 7 09:38:13 ubuntu install.py: self.db.progress('SET', 10 + copy_progress)
May 7 09:38:13 ubuntu install.py: File "/usr/lib/python2.7/dist-packages/debconf.py", line 60, in <lambda>
May 7 09:38:13 ubuntu install.py: lambda *args, **kw: self.command(command, *args, **kw))
May 7 09:38:13 ubuntu install.py: File "/usr/lib/python2.7/dist-packages/debconf.py", line 81, in command
May 7 09:38:13 ubuntu install.py: status = int(status)
May 7 09:38:13 ubuntu install.py: ValueError: invalid literal for int() with base 10: ''