Problems editing files

Hi,

When I try to edit a file on my server and SmartFTP transfers the file only part of the file (about 7k worth) is transfered and the rest is lost.

For file smaller than this there is not problem but for files bigger than this then it seems to only transfer a certain amount of the file.

I assume it is a setting that I need to change, but i'm not sure.

Can anyone suggest anything please??