Martin - as a temporary fix, to get you online again on that PC, go into Control Panel, Add/Remove Programs. Click on the tick box to show updates. Then scroll down to find Security Update for Windows (KB951748). It'll be right towards the end of the updates, as it will be the most recent one. Left click on it to highlight it, and then click Remove.
It'll then remove it (you'll then have to restart your PC).
You should then be online again. Then go to Zone Labs
here, and download the patch file to update Zone Alarm. Then run Windows Update so that it downloads KB951748 again, and you should be OK.