If you get the error message:
File transfer server could not be started or exited unexpectedly. Exit value 0 was returned. Most likely the sftp-server is not in the path of the user on the server side
This is typically caused by unexpected output in one of the user's shell startup scripts, generally .tcshrc or .cshrc. Temporarily renaming the file and attempting to use Secure FTP will confirm if this is the cause.
The problem can be fixed by moving the offending lines to a shell login script (.login for tcsh, .profile for bash).
The offending lines are typically module directives.