Just some simple stuff to check.
Have you rebooted your PC?
Have you checked your firewall? IT might have blocked your program for some reason.
Also, I use www.ftpsurfer.com for preference, it's another free one. Try installing that, I've found it to be realiable.
failing that, check your FTP sockets are open on your firewall, or try changing the socket that might work.
Disable any P2P software that might be working, close as many programs as you can one at a time, attempting the connection after each attempt, this will help you track down any possible culprates.
Also remember, if you are using Windows XP there is a built in firewall, if you are using a router, there is usually a hardware firewall in that as well. Check both.
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