I've been using ZoneAlarm's free firewall for years and always updating when prompted. Got a prompt this morning and did the update (custom install - no toolbar, no default search etc). Rebooted XP Pro to the login/password screen. Clicked my name, entered the password and was greeted with a blue screen: Invalid_Kernel_Handle. Power off and reboot gave the same again.

Rebooted into safe mode, logged in and choose 'System restore'. There was a Restore Point 'Install XP KB943232' which had a date and time around when I updated ZoneAlarm. That got me back to a working PC that I could log in to normally.

I used Control Panel, Add/Remove Programs to remove ZoneAlarm. Googled KB943232, downloaded it and installed it. Rebooted the PC and logged in. Everything OK. (Just to be safe I did a backup of the PC to my Windows Home Server.)

Installed ZoneAlarm as before by running zafwSetupWeb_110_000_038.exe. Finished installation and rebooted. Yes. BSoD Invalid_Kernel_Handle again.

Safe mode and System Restore again. Noticed that I now had two restore points labelled 'Install XP KB943232'. Choose the first one and did a restore. Back to a working PC again. Used Control Panel, Add/Remove Programs to remove ZoneAlarm. Noticed that the size was only 1.7 Mbyte - I'm sure I've seen a much higher figure previously.

So I currently have a functioning PC but no ZoneAlarm.

What gives? Anyone else experiencing this?