What does this mean?

Resolving host name
Connecting to ( -> IP: PORT: 21
No connection could be made because the target machine actively refused it.
Connection closed.

I can't connect to my FTP. What is the problem?

Hi, it can be various things.

1) Firewall bad configured
2) Ftp server down
3) Non existing ftp on that adress

For me works then i think the reason for you can be 1)

I know the FTP address is good. The site may be down. I don't think the firewall has been changed. Should I re-install the SmartFTP?

If you have updated your firewall (for example on windows xp to windows xp sp2) maibe the settings have changed, try checking that you allow SmartFTP to connect.