Avast Internet Security and Simple Workgroup network

I have a network set up with 2 laptops and 1 desktop and 2 printers connected. All computers are running Windows 7 Professional. Everything is working great, but one of the laptops can not be accessed even though it shows up on the network. When I turn Avast Internet Security Shield Control off for 10 minutes, I can access that laptop with no problems. Obviously I have something configured incorrectly. Any help would be appreciated.

please try to change the firewall settings in Internet Security to Private mode instead of Public mode