Having encountered the "compatibility" problem myself, and seen it mentioned alot in response by ZA people, I have to ask- is the supposed incompatibilities problems between various AV and Firewall programs really real?
Before you go off on me, consider this:
1) This post is being made with a computer running absolute latest ZA Pro
installed and patched [to include the fix for MS screw up last week].2) Said computer is also running, fully installed and patched, the latest copy of McAfee Antivirus.3) Both have been installed for many many months, even years.4) Both routinely receive the daily/weekly updates, still. There are no mysterious weird system problems.5) In attempting to build a brand new computer, same fully patched version of Windows XP Pro, both McAfee and ZoneAlarm complain bitterly if I attempt to install one before the other [other doesn't matter].
I have NO problems with either ZA or McAfee on this computer. Fully functional, tested at least weekly.
I am content or even happy with both products, so this is not whinning. I really gotta wonder when the only difference here is motherboard and processor.
PS: Besides, neither of these two companies provide a complete solution to the virus/firewall issue. One detects prior to infection, one blocks inflections taking actions. Someone needs to get their act together.

Operating System:Windows XP Pro
Software Version:7.0
Product Name:ZoneAlarm Pro