Lead differnce between 10g and 11g.

Hello,

We have two databases  the "old" one in 10.2.0.5 and the "new" one  in 11.2.0.2

In each a table filled with the exact same data. 

We run the same query on each table, but we have some differences in the sort order of some rows in result. (10-20 differences on 9000 rows ) 

The NLS on the databases are not the same, could this change some things in the use of the lead function ?

here is the sql :

SELECT

  ID_REFERENTIEL_CANTON,

  REFERENCE_CANTON,

  TRIM(NOM),

  CAUSE_VITESSE_PRESCRITE,

  LIBELLE,

  TO_CHAR(DHM_VITESSE_PRESCRITE, 'YYYY-MM-DD HH24:MI:SS'),

  TO_CHAR( LEAD(DHM_VITESSE_PRESCRITE,1) OVER (PARTITION BY REFERENCE_CANTON_ID