Hi
Using FTP in a web browser has a few special requirements.
Firstly most web browsers if you specify an FTP proxy to use will actually just submit an FTP URL to the proxy using HTTP, and the proxy has to implement a FTP client, and translate the response back to HTTP for the browser.
So generally we recommend using a "real" FTP client that knows about FTP proxies.
Failing that, you can enter a username and password in the URL
e.g.
ftp://user:pass@someftpsite.com/We're working on a new release of 6.5 that solves this problem by sending an HTTP auth request to the browser as well, so this will become easier soon.
Regards
Adrien