Can't ftp from System V to BSD.

[Ellen F Quaadgras]

        I am having trouble ftp-ing from a 3B2 running UNIX System V
to certain systems running BSD (or BSD look alikes such as AIX).
Although I can log into the remote system and do a PWD, I can't use
any commands that require a data connection (e.g. ls, put, get). When
I try, I get the error message : "Can't build data connection." 
        The 3B2 is running WIN3B version 2.1.

        Any ideas that might shed some light on the situation would be
very much appreciated! Thanks in advance...
                -Ellen

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