Javascript error in openerp.base.js

I've just finished to set up an openerp server.

When accessing it through the web-client on my local network everything was runing smooth.

I just put the box in the production environnement where I don't have the network infrastructure under control.
I asked for a port mapping on 8080 and I can access the web-client from the outside.
I can login and i can browser through the top menu and all.

My problem is that the left side menu is not working. It's throwing the following javascript error

Erreur : xhr.getResponseHeader(
Fichier Source : http://xxx.xx.xx.xxx:8080/openerp/static/javascript/openerp/openerp.base.js
Ligne : 112

Here is the http request

Host: xxx.xx.xx.xxx:8080
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; fr; rv:1.9.2.13) Gecko/20101203 Firefox/3.6.13 FirePHP/0.5
Accept: */*
Accept-Language: fr,fr-fr;q=0.8,en-us;q=0.5,en;q=0.3
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 115
Connection: keep-alive
X-Requested-With: XMLHttpRequest
Referer: http://xxx.xx.xx.xxx:8080/openerp/menu?active=73
Cookie: session_id=30b9d45ce3d62aa41a84bdcf0ff6cdfe01848c08; terp_db=xxxxx_dev; terp_user=xxxxx
x-insight: activate

I don't get any http answer the status in firebug is "aborted".

I really have no clue what's happening here.

I hope someone more aknowledged can help me out.

Thanks

ps:
ubuntu lts 10.04 up_to_date
openerp v6.0.1 (both web-client and server, no fancy module installed, all base core module).