Hi, I'm testing this on a 12.04.1 system, since it's a VM I can afford to remove zenity without problems.

First I remove zenity, with checkbox 0.13.7 installed here's what the relevant packages look like:

# dpkg --list checkbox* zenity
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version        Description
+++-==============-==============-============================================
ii  checkbox       0.13.7         System testing application
un  checkbox-gtk   <none>         (no description available)
ii  checkbox-qt    0.13.7         QT4 interface for checkbox
un  zenity         <none>         (no description available)

The test command results in this:
# /usr/share/checkbox/scripts/network_check
Traceback (most recent call last):
  File "/usr/share/checkbox/scripts/network_check", line 64, in <module>
    sys.exit(main())
  File "/usr/share/checkbox/scripts/network_check", line 56, in main
    call(command)
  File "/usr/lib/python2.7/subprocess.py", line 493, in call
    return Popen(*popenargs, **kwargs).wait()
  File "/usr/lib/python2.7/subprocess.py", line 679, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1249, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory


Then in one fell swoop:

# apt-get install -y checkbox checkbox-qt && dpkg --list checkbox* && /usr/share/checkbox/scripts/network_check
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Suggested packages:
  checkbox-cli checkbox-gtk bonnie++ bootchart bzr cvs ethtool flex git-core
  nmap smartmontools sox stress
Recommended packages:
  gstreamer0.10-gconf
The following packages will be upgraded:
  checkbox checkbox-qt
2 upgraded, 0 newly installed, 0 to remove and 248 not upgraded.
Need to get 0 B/1,511 kB of archives.
After this operation, 27.6 kB disk space will be freed.
Preconfiguring packages ...
(Reading database ... 144166 files and directories currently installed.)
Preparing to replace checkbox 0.13.7 (using .../checkbox_0.13.8_i386.deb) ...
Unpacking replacement checkbox ...
Preparing to replace checkbox-qt 0.13.7 (using .../checkbox-qt_0.13.8_i386.deb) ...
Unpacking replacement checkbox-qt ...
Processing triggers for man-db ...
Processing triggers for hicolor-icon-theme ...
Processing triggers for desktop-file-utils ...
Processing triggers for bamfdaemon ...
Rebuilding /usr/share/applications/bamf.index...
Processing triggers for gnome-menus ...
Setting up checkbox (0.13.8) ...
Setting up checkbox-qt (0.13.8) ...
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version        Description
+++-==============-==============-============================================
ii  checkbox       0.13.8         System testing application
un  checkbox-gtk   <none>         (no description available)
ii  checkbox-qt    0.13.8         QT4 interface for checkbox
Zenity missing; unable to report test result:
 HTTP connection: Failed

^^^ Notice that it both reports zenity as missing, and helpfully outputs the test result to stdout. No crashes!

I'll set this verification-done.