V4R5 FTP stalling doing 'GET', 'PUT', etc... - PTF needed?

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We're at V4R5.  I'm attempting to FTP a file to WindowsNT system using the
AS/400 FTP command from a command line.  I can FTP login to the WinNT, but
when I try to 'PUT' a file, or issue a 'dir', or 'ls', or 'GET', 95% of
the time the FTP just sits there with input inhibited on.  (95% is a
best-guess; the send and receive has worked once each out of numerous
attempts).  Eventually the FTP times out with a message: 'No response from
remote host; all connections closed.'

Is there a FTP or TCP/IP PTF that I need to look for, or install?

Tom Hightower
Solutions, Inc
http://www.simas.com