(10:00): There are currently some general routing problems, affecting the majority of the customers at Belgacom. The problems started around 7am this morning. I've contacted Belgacom, and they said the problem would be resolved by 11am.
Unofficially, rumor has it that the police has raided Belgacom because of suspected fraud. Whether this has got something to do with the routing problems is unknown. More details and corrections will follow.

Update (12:00): after careful testing and a bit of a hick-up (routing between Telenet and Belgacom still gave troubles), everything seems to be in   ...