The two parallel entries have to do with Parallels allowing your virtual machine to connect to the internet (most likely Windows).
With Comcast you should not be using DNS entries those should be set to automatic as should DHCP (unless you set static entries for your router and are sure your entry is correct). Basically all settings should be their factory default for Airport. When you connect to your router all information should be supplied automatically.
The only custom settings you need would be for any in network services such as Appletalk, Windows file sharing, FTP, servers, some specialized online services or remote desktop to your work computer.
If resetting Airport to default does not work. Try resetting your router to factory defaults and reconfiguring as they can get buggy. Normally you reset this by depressing a pin hole reset button on the back of the router for 30 seconds while it is turned on (any network security or SSID will be reset as well). At this time you may want to go to your router manufacturers support site to download and install the latest firmware as these are usually buggy on the first revision. You will often get gains in reliability, sometimes you will also get speed or range boosts.