ftp problem

[qstreb <qstreb_(_at_)_ism-computer_(_dot_)_de>]

Hi list,

I'm really sorry to ask so stupid question but it is important for me

I have an openbsd machine (test - current) which is behind
another openbsd (firewall)

from this test machine I can without any problem to write
"lynx ftp.de.openbsd.org" and to see the list of files
"wget -glob=on ftp://ftp.de.openbsd.org/unix/openbsd/snapshots/i386/*"; 
and to get all files from the server

but if I use the normal ftp command 
I will make such an session and after the ls the connection is stopped

$ ftp ftp.de.openbsd.org
Connected to ftp.fu-berlin.de.
220 FTP.FU-Berlin.DE ready, please login as user "ftp".
Name (ftp.de.openbsd.org:root): ftp
331 Anonymous login ok, send anything as password.
Password:
230-
 Welcome at Freie Universitdt Berlin, Germany.
 Willkommen auf dem FTP-Server der Freien Universitdt Berlin.
 Ein Service der Zentraleinrichtung f|r Datenverarbeitung (ZEDAT).

230 Anonymous login ok.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls
500 EPSV not understood.
227 Entering Passive Mode (130,133,1,100,249,213).

421 No Transfer Timeout (600 seconds): closing control connection.

If anybody has any idea what could be the reason for this,
please let me now.

10x in advance,
qstreb