If you find yourself in a situation where you’re using FileZilla 3 and the server is proftpd based you may find that your symlinks (symbolic links) aren’t working and throw the following errors:-
"Critical File System Error"
Then you may need to enable the following in your ProFTPD config providing your ProFTPD server is patched to support it:-
ShowSymlinks on <IfModule mod_facts.c> FactsOptions UseSlink </IfModule>
Hope this helps