After trying out the markUp-plugin by Rick Cockrum (as he suggested before), my Habari install first crashed with a PHP memory allocation error when trying to create a new post oder page, later on did only send empty (blank) pages - after I removed all of the markUp-plugin data and references.

I'm posting this using phpMyAdmin, but am going to update to the latest 0.6alpha during the next few days to fix this problem.