German conversation table?

Ja klar! Aber sicher! Kein Problem! Sauerkraut!

Firstly, there are a number of German meetings from Anonymous Alcoholics to Seniorengruppe listed here: http://www.belgieninfo.net/?id=158
The "Cercle Polyglotte" might be what you are looking for.

Secondly, you could organise a meeting yourself, which actually is pretty easy. There are two "social activity" websites I would like to recommend:

"On va sortir" gives you the possibility to propose any sort of social activity, incl. language exchanges. You set the time, place etc. and others subscribe: http://bruxelles.onvasortir.com

Then there is Meetup with a bit of a different principle, since it is organised in groups and only members of the group are informed about upcoming events, so less ideal for your purposes:
http://www.meetup.com/cities/be/brussels/