Then you might try upgrading to the latest version (1.24), it might be a bug, but before contacting DirectAdmin, try to explore all possible possibilities.
I can download databases through Directadmin in 1.24 and FreeBSD 5.3, however there seems to be an upload problem reported by one of my users which I havent investigated yet, this was reported before I upgraded to 1.24 and unconfirmed.