I found this in the Event Log:

Event Type: Error
Event Source: Service Control Manager
Event Category: None
Event ID: 7031
Date: 04.12.2005
Time: 11:11:12
User: N/A
Computer: KAARELA0
The TrueVector Internet Monitor service terminated unexpectedly. It has done this 1 time(s). The following corrective action will be taken in 0 milliseconds: No action.

My ZAPro is 6.1.737

Operating System:Windows 2000 Pro
Product Name:ZoneAlarm Pro
Software Version:6.0