FTP Problems with network and firewall

Hi,
We have a mixed network of Novell and Sun servers along with a firewall (maker I don’t know). I use Epsilon for windows to access most of the files I edit on the Sun machines using the FTP client built into Epsilon. All of a sudden I can’t access machines that are in the firewall with Epsilon’s FTP but I can with other FTP clients (like WS_FTP Pro). When I try to connect I get the following response in the Epsilon FTP log:

000 Connecting to pubtest1
220 pubtest1 FTP server (SunOS 5.6) ready.
USER dfarrell
599 Control socket to pubtest1 unexpectedly closed
QUIT

Anyone have any ideas on what’s going on and more importantly, how I can fix this?

Thanks in advance,
Doug Farrell