[apport] gnome-app-install crashed with ImportError in <module>()

I tried to upgrade to the version 7.04
During the process of upgrading many bugs were mentioned, I didn't care about. I tried again many times.
Today, surprisingly, the upgrade to the version 7.04 succeeded partially.
I tried to reinstall the software "tomboy" with the application : Ajouter / enlever (add / suppress).
The application didn't open.
I tried then to open the application "synaptic", which did'nt accept my password.
I don't know how to debug all my system and to clean up my system. As an analphabet in informatics, I did many risky manipulations.
Thank you and best regards.
Pierre Bonvin

ProblemType: Crash
Architecture: i386
Date: Fri Apr 27 18:22:28 2007
DistroRelease: Ubuntu 7.04
ExecutablePath: /usr/bin/gnome-app-install
InterpreterPath: /usr/bin/python2.5
Package: gnome-app-install 0.2.21
PackageArchitecture: all
ProcCmdline: /usr/bin/python /usr/bin/gnome-app-install
ProcCwd: /home/fuma
ProcEnviron:
 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/bin/X11:/usr/games
 LANG=fr_CH.UTF-8
 SHELL=/bin/bash
PythonArgs: ['/usr/bin/gnome-app-install']
SourcePackage: gnome-app-install
Traceback:
 Traceback (most recent call last):
   File "/usr/bin/gnome-app-install", line 137, in <module>
     from AppInstall.AppInstall import AppInstall
 ImportError: No module named AppInstall.AppInstall
Uname: Linux fuma-desktop 2.6.17-10-generic #2 SMP Tue Dec 5 22:28:26 UTC 2006 i686 GNU/Linux