I second TBNs reccomendation on that thread; I have a special fondness for A l'Imaige de Nostre Dame. I think that was where I had my "St Paul on the road to Damascus" event and started drinking real beer. I have been annoying my friends in pubs since; just can't make up my mind whether to drink Guinness or Smithwicks - awkward fecker!
They had (and probably still have) Bourgogne des Flandres on tap (only 2 pubs in Brussels do). It's a Flanders sweet/sour ale.
The pub itself (opens at 4pm) is an oasis of quiet down an alley near enough to Bourse.