apt-check crashed with ImportError in <module>()

Binary package hint: update-notifier

just used update manager to update everything (looks like the update included some new apt, apt-util, synaptic, aptitude packages) .. after I updated i clicked 'check' in update manager again for kicks and the update-notifier task crashed.

ProblemType: Crash
Date: Mon Feb 26 20:03:24 2007
DistroRelease: Ubuntu 7.04
ExecutablePath: /usr/lib/update-notifier/apt-check
InterpreterPath: /usr/bin/python2.5
Package: update-notifier 0.56
ProcCmdline: python /usr/lib/update-notifier/apt-check
ProcCwd: /home/droptic
ProcEnviron:
 LANGUAGE=es_CL:es
 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
 LANG=es_CL.UTF-8
 SHELL=/bin/bash
PythonArgs: ['/usr/lib/update-notifier/apt-check']
SourcePackage: update-notifier
Traceback:
 Traceback (most recent call last):
   File "/usr/lib/update-notifier/apt-check", line 6, in <module>
     import apt_pkg
 ImportError: No module named apt_pkg
Uname: Linux compaq 2.6.20-8-generic #2 SMP Tue Feb 13 05:18:42 UTC 2007 i686 GNU/Linux