Currently Being ModeratedFeb 5, 2013 12:16 PM (in response to Robert Glimmerud)
As a first step, just reboot the TC and laptop.. Apple has been less than stable on its network since Lion. And ML is much worse.
If you still get connection to the TC but not internet it usually will be caused by failure to pick up the gateway address.. (router IP in apple speak) or the DNS. Open the network preferences under the airport fan and check the full set of info is there.
Check the difference between the working units and the one that doesn't.
If the laptop was upgraded to Mountain Lion for instance the wireless can behave poorly.. test it with ethernet.. if it works fine then I would recommend a clean install of the OS.. which I know is a pain but gives much better results.
You can try using statically set values if any are missing.. for instance DNS try using 18.104.22.168 which is the google dns and if that works shows the laptop is not picking up DNS correctly.