Wont Connect To Any FTP Servers

When I try to upload a large sum of of files using 1 worker on an ftp server it will upload a few then just stall and it will keep retrying to upload them. I close Smartftp and re-open it to find that it wont connect to ANY of the 3 different FTP servers. The other ftp servers worked fine before the restart and are completely different than the one that stops uploading. I dont run any firewall, im on a router but it never blocks anything (Apple Airport Extreme), I have ESET but I put in an exception for smart ftp. Im running the latest x64 version. It says the following for each ftp server on connect.

[15:12:11] Connecting to Port: 21
[15:12:12] No connection could be made because the target machine actively refused it.
[15:12:12] Connect failed. Waiting to retry (30s)...
[15:12:12] Client closed the connection.

Eventually it reconnects to each server after retrying for a few minutes including the one that causes this.

Might be an issue with your software firewall, antivirus product, router or server.
Try to connect with the command line ftp client (ftp.exe) when the problem happens.