Why does my wireless LAN stop mid session

I start up in the morning and everything is fine, but at some point during the day, my wireless LAN quits. I've changed modems and routers but I still have the problem. My provider sees nothing on his end and other computers on my home network work fine. When I turn the wireless off and back on I get a new lease on wireless until it decides to do it again. I'm running the latest OS X 10.8.2 (3.1 GHz Intel Core i5) with 4GB 1333 Mhz DDR3. Has anyone had this problem and if so have you found the solution. Thanks!