problem with permalinks on modified pages

hello
this is my first post, so here is my config :

– WordPress version: 3.1
– Host : privianet
– PHP/MySQL : 5.2.6 / 5.0.51a
– Theme : apricot (very)modified / mineral
– website 1 : boutiquemetiersdart.fr
– website 2 : lespierresparlent.info

now the problem is :

permalinks are activated with the custom option “/%postname%/
but for certain pages the URL that appears in the navigator’s adress bar contains obsolete names of the pages
example : this page where you can see in the URL “le-projet” instead of “le-reseau”. it’s amazing to see “le-projet” which was the title of the page 4 months ago, and not “le-reseau” which is the present name of the page.
NB : the problem occurs in the subpages too.
the question is : how can I fix that ?

thanks for your help…