Try changing your MTU from the stupidly default 1432 to the maximum 1500. I had exactly the same issue, and after an hour on the phone to Belkin support, we eventually tried changing this value and all FTP access is now working fine.
Hi - saw moggoly post. I have cable internet rather than DSL. Is MTU still relevant with cable? If so - do you know how I can change it? I have same issue where I can't FTP