Wing FTP Software

When using the command window (cmd.exe) issuing the following commands:
ftp server.com
enter username xxx
enter password xxx
user logged in.
the first command issued ls or dir - returns Illegal IP address for the PORT command
additional attempts of ls or dir - returns Bad sequence of commands.

I don't have any problems with the FTP server using a windows based client or HTTP just from a command prompt.

Any ideas?

Yes, if your FTP client is behind a router/firewall, then FTP server can't connect to it normally. You can paste the related server logs, I guess it was caused by similar reason.