I had ridiculous trouble with ZoneAlarm. It was just terrible. When I tried to get rid of it, something happened, and a lot of the programs that ran in the background were left over and still ran, even though most of the program was uninstalled... have you tried uninstalling it in safe mode? thats how i finally got rid of it...
as for a new free firewall, i'm not totally sure...
AMD 64-bit 3400 @ 2.2Ghz
MSI - K8N Neo Platinum Mobo
BFG GeForce 6800 GT (3Dmark03 - 11,518)
Corsair XMS 1024MB (512 MB x 2) DDR 400