pybackpack crashes after clicking "Go"

$ pybackpack
Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/pybackpack/gui.py", line 131, in on_combo_backup_sets_changed
    for row in self.drive_sel.get_model():
AttributeError: Gui instance has no attribute 'drive_sel'
Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/pybackpack/gui.py", line 208, in on_button_do_backup_clicked
    self.do_cdr_backup()
  File "/usr/lib/pymodules/python2.7/pybackpack/gui.py", line 245, in do_cdr_backup
    if self.drive_sel.get_active() == -1:
AttributeError: Gui instance has no attribute 'drive_sel'

I got this traceback after clicking the "Go" button.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: pybackpack 0.5.8-1.1ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-25.40-generic 3.2.18
Uname: Linux 3.2.0-25-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.0.1-0ubuntu8
Architecture: amd64
Date: Fri Jun 29 17:56:27 2012
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 10.04.3 LTS "Lucid Lynx" - Release amd64 (20110720.1)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, user)
 LANG=en_CA.UTF-8
 SHELL=/bin/bash
SourcePackage: pybackpack
UpgradeStatus: Upgraded to precise on 2012-04-28 (62 days ago)