cannot connect through socks5/proxy

I really need somebody' help.

My computer is the one of three of PC through proxy server. I used to
be no problem with using smartFTP. However, all of a sudden, my computer can't be connected through smartFTP.
I have no problem with messager and internet connection, though.

The error message is
" SOCKS5: Got no response from firewall. Session aborted."

How shall I solve this problem ?
I tried every version of smartFTP recently.

Please reply !! :cry: