Hey, sorry for the late respons. I had to wait for my neighbours to get access to their computer so I could test the client side with them. Anyway it still isn't working. I tested several options:
I disabled the firewalls on server and client side;
I opened several ports;
Also placed the server at my neighbours and made myself a client, so I could test their router.
Anyway the next link shows a image of my router configuration, the lowest line is what I use for my gameserver.
http://img167.imageshack.us/img167/2441/naamlooskr9.jpg

Hopefully someone can tell me what I'm doing wrong.
Thanks anyway,
Molotov.