[Mediawiki-l] database did not find the text of an existing page after upgrading from 1.11 to 1.14

[Frames Project]

Hello

I tried to upgrade from 1.11 to 1.14.
All operations have been done locally with the Mediawiki tools.

The details of the procedures are given in the wiki page :

http://comprendrelactualite.free.fr/mediawiki/index.php/Mediawiki_Upgrading_WikiCla_from_1.11._to_1.14
(log in and comment please)

Everything seemed to be ok. 
Nevertheless, when checking some (not all) pages at random, while the
page name is correctly provided by the wiki, the page text is empty and
I got the following error message, that I do not understand :

        La base de données n’a pas trouvé le texte d’une page qu’elle
        aurait dû trouver, intitulée «XXXX» (révision # : 2485).
        Ceci est habituellement causé en suivant le lien périmé d’un
        diff ou de l’historique vers une page ayant été supprimée.
        Si cela n’est pas le cas, vous pouvez avoir trouvé un bogue dans
        le programme. Veuillez en faire part à un administrateur et lui
        noter l’adresse cible du lien.

which could be translated by :

    the database did not find the text of a page that it should have   
    found, named « XXXX » (révision # :2485)
        This is usually due to following the obsolete link of a diff or
        of the history to a page that has been removed.
        If this is not the case, you should have found a bug etc...
        
1. Why this error occurs ?
2. What could I do to fix it ?

Thanks
Francois Colonna