FTP - Sco Unix to ProFTPD Error

First off I did try google for help on this topic, didn't really find anything.

When I try to ftp from my SCO Unix box (SCO_SV servername 3.2 5.0.5 i386) to a proFTPD server within my company I get this error

Connected to 10.?.?.?.
220 ProFTPD Server ftp.hostname.com
Name (10.?.?.?:root): ftpusername
504 AUTH KERBEROS_V5 unsupported
Login failed.
Remote system type is unknown.
Using ascii mode to transfer files.
ftp>

I can connect to the FTP server no problem with smartftp or even command line in windows.

Any help would be great.

Thanks

Found on Cert advisory CA-1996-03

This would seem to imply that unless you have/get the add-on product, you can't do Kerberos V5(or any other) support which is why your ftp is failing.