Uploading Problems

I'm having problems uploading from one site to another. I'd like to get some files over through one websites FTP, to another websites FTP.

What should I do? I keep getting an error like "Illegal Port Command" when I try to upload some pictures from the site into my directory. What am I doing wrong, and how do I transfer from one sites FTP to another?

Both hosts have to support PASV mode and must allow PORT commands to foreign hosts.
Are you sure they are capable of doing that?