For as long as Zonelabs has been in development of Zone Alarm you would think they would have the bugs worked out by now. I used it many years ago and it was so bug ridden I moved on to other products. I decided to give Zone Alarm Pro another shot this week and purchased and installed it and I see they still have not worked out the bugs.
I spent two days trying to overcome problems with Zone Alarm, things like it all of a sudden closing the internet connection on applications that it had previously allowed to work, not allowing my computer to shutdown but hanging on the Zone Alarm program and telling me it's not responding. Allowing applications to work properly for the most part but would not allow one certain part of the application to access the internet. For example, it would allow firefox to browse the web but would not allow it to check for updates to the application.
I am familiar with the setup of personal firewalls and rules creation and I ensured that each application had full access and was allowed internet access. I requested help and was directed to some "work around" instructions to try and force the program to work.
A quick scan of the Zone Alarm Forums show others are equally as frustrated.
It is surprising that a product of this maturity would be so full of bugs and problems. It seems by version 6 you would have the basic firewall functioning reliably.
I had resigned myself to sticking with the Windows XP build in port blocker (otherwise knows as a firewall), however, thanks to this newsgroup I stumbled upon a free firewall called COMANDO. There is a lot of traffic in this newsgroup about this application a year ago but it's quieted down recently so I decided to give it a try. So far it's worked as I would expect a personal firewall work. I'll let you know after I get more time with it.
Anyway, just wanted to give my impressions of my recent experience with Zone Alarm Pro.