Something is turning off my Sunbelt personal firewall!

I keep discovering that Sunbelt (Kerio) Personal firewall (I have version 4.6.1861 installed in the free version) has been deactivated or turned itself off -- with no warning!

And I have no idea how long it has been turned off, and how long I've been conncected to the internet without a firewall.

Running various free anti-root kits (from sophos; gmer; spybot; avg; fsecure blacklight; avira; panda; rootkitrevealed) has never revealed a rootkit; spybot seach & destroy and avast have never revealed any serious infections that they couldn't readily deal with,

--yet I keep suddenly discovering that Sunbelt's icon is no longer present in my system tray at the bottom of the screen -- and in fact, sunbelt doesn't seem to be running or active at all anymore -- because it's no longer intervening to ask me whether I want to allow various processes to be run by various programs or not -- but I never have any idea how long it's been shut down, or what caused it to stop, and how long I've been exposed to the internet without a firewall!

(Restarting the computer then activates sunbelt again, but I want to know how to make sure it stays on!) Can anyone help me?

(I'm running Windows XP Home Edition, Service Pack 3)