Xen guest installation failure following prompt

[Cerin]

The binary "virt-install" is nearly completely inoperable when using the --prompt option. It appears to be encountering a Python exception.

myuser@localhost:~$ sudo virt-install --prompt
[sudo] password for myuser:
Would you like a fully virtualized guest (yes or no)? This will allow you to run unmodified operating systems.
yes
What is the name of your virtual machine?
newmachine
How much RAM should be allocated (in megabytes)?
2048

Starting install...
ERROR 'NoneType' object has no attribute 'startswith'
Domain installation does not appear to have been successful.
If it was, you can restart your domain by running:
  virsh --connect xen:/// start newmachine
otherwise, please restart your installation.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: virtinst 0.600.0-1ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-12.20-server 3.0.4
Uname: Linux 3.0.0-12-server x86_64
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
Date: Sun Feb 19 04:37:55 2012
InstallationMedia: Ubuntu-Server 11.10 "Oneiric Ocelot" - Release amd64 (20111011)
PackageArchitecture: all
ProcEnviron:
 SHELL=/bin/bash
 LANG=en_US.UTF-8
SourcePackage: virtinst
UpgradeStatus: No upgrade log present (probably fresh install)