Hi,
I am pretty sure you know far more than me regarding ftp, but since there have been no responses to your question, I would ask a few questions to maybe help determine where the difficulty lies. First, when you enabled the ftp function on the 320 did you leave the default settings or make any changes. You might try the default first. Next, have you tried to access the 320 via Internet Explorer or if you use Firefox, have you tried Fireftp addin? If so, can you connect both from within your network and from an outside / remote location. These are some of the simplest and least complex methods to log into an ftp server and both work well with accessing my 320. If you cannot access the 320 from within the local network, it would be either the 320 or perhaps the network settings. If you can reach it locally, but not externally, then if would point to either the router, or maybe the settings in Filezilla. That's about all I can think of right now. Good luck.