FTP connects with DSL but will not connect with T-Mobile home.
Do you have a different firewall with that router that could be interfering? That is where I would start. Also if you click on Site-->Advanced-->FTP Log next time you try to connect and report the error number that will tell us exactly what is happening.
Evidently this is known problem for T-Mobile users.
Hope that helps. If not, a Google search for T-Mobile can't connect to FTP will likely yield other things to try.