Although this has been posted,
it's hard finding it in a search or by looking on the forum quickly, so I wanted to post again because it seems to happen right after installation the update of ZoneAlarm 7.0 with a licensed version or free version.
I have a free version running and it does the same thing:After installing the update and opening Microsoft Outlook 2003 it would say that there was a serious error that occured when closing and that the mailbuddy outlook addin needed to be disabled to open properly.
If you disabled it, then you had no problems but then you could not re-enable without getting the same message again.I found this link message that intructs to re-set the original settings and then enable the addin and IT DOES WORK.
Hopes this reaches others faster.

Operating System:Windows XP Home Edition
Product Name:ZoneAlarm (Free)
Software Version:7.0