I replaced the router at home and ran into problems FTPing to my home FTP server. Specifically, I can't get a directory listing when I connect to my home server. There are no problems when I FTP to other sites.
The problem may be with a CoreFTP setting because I was able to get a listing by using the XP built-in command line FTP. After logging in, I did a DIR command and immediatelt got a listing.
The router replacement was a Netgear WGR614. When I tried to open an FTP connection it didn't complete. I discovered that the port forwarding on this router didn't allow me to set start port to 21, which is necessary because I need to operate in PASV mode. The Netgear help line had me delete the FTP port forwarding and create a new port forwarding service (which I named TFP) starting and ending on port 21. Using that setting, I was able to open a connecting using CoreFTP. I observed the opening on the server. I even saw the LIST command received at the server. But I never got the file listing displayed on the CoreFTP client. As I said, I was able to get the listing using command line FTP.