Accessing FTP on NT 4 Server

I set up FTP services on our NT 4.0 Server, set up Virtual Directories to point to my web folders to enable uploading update files to several websites, and established permissions. It was working fine, and I was able to upload to the individual web folders using WS_FTP. Then I had the name of the server changed on the DNS server. Now, when I try to upload using WS_FTP, I can’t get a connection. I connect to the server, but I can’t seem to get past port 21. It hangs, and I get an error message reading “Receive Error. Blocking Call Cancelled. Connection Failed”. I’ve tried recreating the virtual directories and the Default FTP Site, but nothing works. I also tried using another IP address. Nothing works. Anyone have any suggestions?