Gaming kills my internet connection

I have XP Pro with SP2. My internet connection is cable through a PCI card. I am also running Zone Alarm free version as a firewall, and use a wireless router. Often after playing a computer game, my internet connection stops working (although it works fine for online gaming.) Sometimes it comes back after waiting a while; more often I need to reboot the system to get it back. What could be causing this? I don't think it is ZA because shutting it down does not restore the connection.