I also have the same problem.
Installed Zone Alarm Pro 9 yesterday and now my computer reboots on its own at random.
It has rebooted 3 times today so far while I'm typing.
No warning is given. Just the screen goes blank and Windows reboots.
I'm using Windows 7 64 bit. Also installed Avira Antivir at the same time, but as others are reporting random reboots I think the problem is with ZAP.
Unless there's a fix, I'll have to uninstall.