ASTK error with script

Hello,

I am trying to use ASTK. I am taking some examples insides tutorial but I have always this error :

'import site' failed; use -v for traceback
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/opt/aster101/lib/python2.6/site-packages/asrun/main.py", line 25, in <module>
import os
ImportError: No module named os

I have CAElinux version 2010 with no modifications.
My PC is 64 bit optiplex 740 (dell)

It seems some configurations problems. Any idea ?

thanks,
emmanuel