Template images corrupted during FTP

I have installed Zen Cart 1.3.8 to a server using Fantastico.

Every time I try to upload a template via FTP (using Filezilla) images files (.gif) are corrupted.

The files on my desktop are good, but by the time they get to the server they are scrambled. If I download them, a view them again, they are seriously corrupted.

I have successfully installed other things (e.g. Image Handler 2) without problems - it's only templates with .gif's that mess up.

Is there something wrong with my FTP settings?Please don't suggest alternative FTP clients, as I use Ubuntu Linux.

Any Filezilla gurus out there, please?

Oops - solved my own problem by noodling about.

If you have the same trouble, open Filezilla & go:

edit --> settings --> FTP.
In the 'Transfer Mode' box make sure the 'Active' radio button is selected.

Works for me - just wish I knew why!