I had exactly the same problem
running version 6.5.737.000
I ended up uninstalling Zonealarm via add/remove programs and reinstalling.I turned off auto-update as apparently the problem may be due to Zonealarm updating itself whilst Outlook Express is open.(See this link to another thread on here - http://forum.zonelabs.org/zonelabs/b...essage.id=7375)
So far I haven't had a repeat of it yet and I just manually update once every few days and I have had no probs with any other functions.
Hope this helps - but as the other thread states - Zonealarm should have dealt with this issue - perhaps they have in version 7!!!