If you have Zone Alarm version 6, you may experience problems due to expired certificates relating to dll files.
They expired at midnight on 15th July (last night).

Here's what to do:

Method 1 - change the date on the system to 15th July or before, restart. Then uninstall ZA and replace it with the latest version.

Method 2 - might be needed because ZA leaves behind a lot of stuff after uninstalling (even using Revo to do it.)

Start up in Safe Mode and then uninstall ZA. Stay in Safe Mode and remove these files:

From C:\Windows\System 32, all of the following files,
vsdata.dll
vsinit.dll
vsregexp.dll
vsutil.dll
vsxml.dll
zlcomm.dll
zlcommdb.dll
vsdatant.sys

plus Zone Labs Folder

From C:\Windows - remove Internet Logs folder

Now install the latest version.

Version 6 must be a fairly old version isn't it?

It has been quite a while since I last updated ZA, but I seem to be on version 8 in both XP and Vista.

Last updates to version 6 were in 2006. I've also been installing the older version during the past two years.

I've learned a lesson about updating .....................