Ftp Issues

Ok so ive had this problem before on another computer but now it works on the other computer (after i reformatted) and on my new computer it wont work. I use SmartFTP and i can connect to the server view the files and dl them i just cant upload, it will upload however it just times out and leaves a 0kb file in replacement of the file that i was trying to upload. Does anyone know how to fix this?