> when i do a: -N "%[lang]/%p/%n%[node].html" option.. i
> obtain  something like fr_/home/home1.html and that's not

Yes. In fact no, this is not really a bug.

Actually the path (%p) is the "absolute" path ; that is, 
something like:
/home/home1.html

In this case, because of the supplemental "/", the formed 
path is:
fr//home/home1.html 

.. and httrack "cleverly" replaces the second "/" by _ to 
fir the local filesystem restrictions.

Hence, use:
-N "%[lang]%p/%n%[node].%t" 

(Note: when there's a missing "/" at the begining, httrack 
adds it automatically)