I have this problem on all my 3 PC's, running XP professional and one XP home.
Clean uninstall and new install solve the problem for about one week.
I try a "reset to default" and change only some setting eg. "drive to check" and my "Zonealarm extreme Seccurity Version" is running perfect for more than on week.

Checking my old setting against the default settings now gives no results. I assume that internal settings (not available through the userinterface) are the problem.

I hope other users having the same error try the same and give some results at this thread.

Rgds. Klaus from Germany