Cannot start nav

Hello. I cannot figure it out why i cannot start nav 3.5.4. It is installed on a Ubuntu 9.10. I’ve done all the steps in INSTALLATION and getting_started_guide files.
This is output :

/usr/local/nav/bin/nav start

Fatal error: Could not find the nav.startstop module.
Is your PYTHONPATH environment correctly set up?

And …

echo $PYTHONPATH

/usr/share/python/

Any idea? Thank you!

It seems your system having virus problem. so first of all clean your system with some licence version anti virus after that reinstall this set-up.