CFtpConnection in passive mode problem

I've been searching every where for answers to this, hopefully some one here will have an answer.

I have an application that must transfer files from a remote server to our central FTP server. Some of these remote sites require the passive flag, while others do not -- not certain why or how to change them so that passive is not needed.

On some of the sites where passive is required, it seems that setting the passive flag is not enough. The file gets created on our FTP server, but that's about all. The file never gets transferred and all I get on the FTP server is a zero-sized file. Again, don't know why.

Any help would be appreciated