Old skool! Without the aid of those nice graphical front ends!
http://www.computerhope.com/software/ftp.htmBasic help (I'm assuming your running Windows?)
In theory, your GUI app is doing the same thing on the underlying protocols.....
If a 'DOS' FTP fails then one of two things...Either your end is causing issues, firewall, router etc...or your host is having issues of some description. I guess another quick test maybe to see if Creech can upload an image?
I suspect it would be the GUI, as FTP does not really care what the file is, as long as it contains 1 & 0's!