Hi Jeff,
alas you are assuming facts not in evidence <g>..
a) given that the problem manifests on some computers, but not others implies either a timing issue, or a firewall issue. Testing against the _server_ (not the client) from here either eliminates or exposes the problem. Best case I get it here, worst case I don't - both outcomes tell us something.
b) I don't need access to the client at all (and frankly that's not terribly useful to me to start with - maybe later it's an option but not necessary now.) what I need is the name of the FTP server you are using, plus access credentials, plus (ideally) an explanation of which file you are trying to download.
But then again - only if you want help - if you'd like to continue pursuing it on your own you're welcome to do that of course....
cheers
Bruce