Cannot FTP from one networked PC

[#1]

A desktop and a laptop both run XP. They are linked in a home network, by two “home plugs”, with the desktop having a direct ADSL connection.
I used to be able to FTP from both machines, and I have not made any conscious changes, although some programs have been updated.
The symptoms are:
    * Both can access websites via browsers
    * Laptop can FTP via a client application - WSFTP
    * Desktop cannot FTP, with FTP Commander or WSFTP (“Winsock 10080 – timed out”  message)
    * Desktop cannot connect to the FTP site from the Command prompt, ie before name and password are requested
    * Desktop can ping the site by name or IP)
Desktop runs ZoneAlarm firewall, Spybot, Windows Defender and Norton Antivirus. Disabling ZoneAlarm has no effect. Both Windows firewalls are turned off. Laptop runs Bullguard antivirus and firewall.

Any ideas would be gratefully received.

[#2]

I think a Winsock 10080 error implies a resource deadlock occurs. Are you trying to FTP through your laptop and desktop at the same time? What happens if you turn off the hardware, then try again with the laptop left off?

[#3]

I only attempt to FTP on one machine at a time. Having the laptop switched off makes no difference.