"Established connection aborted by software on host machine"

I have just installed SmartFTP and get the message "Established connection aborted by software on host machine" when trying to connect to a website I have connected to successfully using SmartFTP on a different machine. My first guess is that I am running BitDefender antivirus software and it might think this is a phishing incident, but I turned off Phishing protection and still can't connect. Any ideas?

It turns out the problem was not on my end, but with the server for the site I was accessing. So...never mind.