After many months being unable to download or update any Zone Alarm security updates - and trying all manner of methods to sort it out - I downloaded SUPERAntispyware Free Edition and it picked up 3 trojans and fixed the problem after one scan! I have XP Home Edition and ZA full security suite. Hope this helps others in the same boat ...

Operating System:Windows XP Home Edition
Software Version:8.0
Product Name:ZoneAlarm Internet Security Suite