[AccessD] OT: Firewall

I\'m having a huge problem getting Zone Alarm on one of our computers   I've used it for years with no problem, upgraded this one box from Version 3 to the latest, it blocks internet access and give a page full of instructions on how to solve the problem - none of which work.  

Uninstalled, reinstalled,  cleaned registry per their instructions, renamed the internet log, blah, blah.

At the moment the machine is behind the router firewall (like all of them) so I don't know if I should be too concerned but I've always run a firewall on each machine in addition to the hardware firewall in the Linksys.

I'm not wedded to Zone Alarm and I'm looking at Sygate's product ( another free one : http://smb.sygate.com/products/spf_standard.htm) .  Anyone know about this?  Any other recommendations for a personal firewall?

Thanks and regards,

Rocky