First you need to make sure that you have ftp access enabled for external clients, "from outside your local network". Go into the "e-smith-manager" under remote make sure FTP user access is set to Public.
Next go into the properties for the Ibay, there should be a group that has been assigned to this ibay. If it just says "Administrator" you have not created a group that is associated with the ibay. I have a feeling this is your problem. Next you want to create a group, add your users to that group. Then in your ibay properties change the group from "Administrator" to "the group you just created".
Then of course you need to modify the settings on the Ibay page that will allow you write access for the group, etc, etc.
I hope this helps out.