I would try to ftp into your xbox using Internet Explorer. in the address bar, type
ftp://(Your Xbox's IP)
Then it will pop up with a login screen, you should enter the username and password that you set in the dashboard settings, if you haven't changed any settings, then just enter in xbox for username and xbox for password. Alternatively, kinda quicker, you can just enter in the username and password in the address, like so...ftp://username:email@example.com
Hope that works. If that works then its the ftp program you are using...