Cannot upgrade past 1.33.4

Hi,

I've been asked to upgrade a very, very old wiki : it was version 
1.25.6. I decided to do it step by step, ie release by release.
I carefully backup-ed the database between each iteration, and ran 
maintenance/update.php

Everything went fine until 1.34.4, when the vast majority of links were 
broken (Page does not exist yet)

There were some stopper between 1.33 and 1.34 ? I read the release 
notes, update.php is intended to do the right job

Thanks for help,

Cheers,

Xavier

-- 
Xavier Humbert
CRT Supervision et Exploitation de Niveau 1
Rectorat de Nancy-Metz
03 83 86 27 39