FireWall and FTP server question

["Alex V. Toropov" <alex@ct.spb.ru>]

Hi all,

I have an FTP & WWW-server behind my firewall.
This firewall allow any tcp trafic from/to ports 21 and 80 of this
machine. WWW-server works fine, but connection to FTP-server
hangs after user authentification (on first LIST request from client).

As far as I know FTP needs some other port for DATA connection.
I've tried to open port 20 on firewall as well, but it dosn't solve
problems.

Please tell me at what point I'm wrong?

best Regards, Alex

PS My ftp server is ftp.ct.spb.ru - if someone would like to examine
problems.