Problem solved:

Had to un-comment the line with the memory limit in the /conf/_advanced file.

But then b2evo still wouldn't update. It stopped while updating the hitlog table. Without error message.
Problem: The hitlog table was quite big and so I emptied it. Database update went smooth after that.
My site is now online again and I can start working with 3.3.1! Looking forward to it!

Why didn't you just put 128M there instead of emptying the table ?

Actually I think "empty your hitlog table by deleting all your daily hits (on the stats tab) BEFORE doing your backup and upgrade" should be standard procedure for an upgrade or movement. I'm pretty sure that action will also dump tons of stuff from the sessions table as well, so you start the process with cleaner tables. Easier to back up, easier to restore, and removes one known choke point in front of an upgrader.

Updating from 2.4.6

Fisrt part of the update went well, but the i had the same exact problem has above, since i don't have anymore access to the backend.

I wen to phpmyadmin to clean up the hitlog table.
after that it went 1 step further :

Loading: _core/model/__core.install.php
Loading: sessions/model/_sessions.install.php

Vérification de la version du schéma BD... 9800 : OK.
Updating keyphrases in hitlog table... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

so i'm having these dots by tons, my page is huge filled with dots.

any idea what i can do ?

edit : it's done :

Loading: _core/model/__core.install.php
Loading: sessions/model/_sessions.install.php

Vérification de la version du schéma BD... 9960 : OK.
Resetting b2evolution.net polling times... OK.

Le schéma de base de données est à jour.

Mise à jour terminée avec succès!

Those are kinda progress dots :) you get a dot for each converted keyword.