Using vsftpd on the SuSE Linux 10.0 server, some clients are unable to list directories once connected while others work just fine. Very strange since FTP has only been around for decades

Basic functionality should be working right by now!
Windows and SCO Unix work perfect with no user intervention.
NetBSD and FreeBSD will work if set to active mode before connecting.
Mac OS X and other SuSE Linux boxen will not work at all! They give a "Entering Extended Passive Mode" or something about "EPRT" (depending on passive/active mode) message, then just sit there.
Tried it with all firewalls off and that changed nothing. There's no filtering device between them. Googled around for several hours already and encountered lots of other people with the same problem, but no solutions (other than a couple cases where turning off firewalls helped).
Help me before I have to resort to moving the website over to a Windows server!