MacBook Pro with Mountain Lion losing Internet Connectivity

I have a MacBook Pro (mid-2011 model) running 10.8.2. I have Suddenlink internet that uses a cable modem that is plugged into one of the new Airport Express Base Stations. I allowed the wizard of Airport Express to automatically setup the wifi network. I have a MacBook (2008 model), two iPhone 5s, an Apple TV, and 3 iPads also connecting to the network. Those all work just fine. However, on the MacBook Pro, it seems to occasionally have a hiccup that loses connection to either the internet, wifi network, or both. I first discovered this when switching between libraries on the Apple TV. It would show in the list of libraries, but when switching to it, it would say it was not available. If I tried to surf the web at this time, it would tell me it was not connected to the internet, even though the Wifi signal strength showed as excellent and connected. I have tried resetting the modem, restarting computer, restoring Apple TV, and restoring Airport Express, each multiple times. After a reboot or reset, it will work well for a few hours, and then have to do it all over again, or wait for the internet connection to reset itself. Any suggestions?

I have a 2012 MacAir running 10.8.2 and have been having problems with wireless connectivity since I starting using it in July. Not so much a problem with connecting, rather it would take forever to connect and often simply not without reboot. The seeming cure for my situation was to shut off airport, open key chain, and under Key Chain menu, choose First Aid and run repair. It spotted some errors and fixed them. Upon turning on Airport, I have had no problems since. My wife has a 2011 MacAir and has had no similar problems.

Good luck