I just bought a new Mac Book Air 11", but it looks like it has a problem with WiFi. So, every 20-30 minutes I lose an internet connection. The WiFi signal strength is good and adapter doesn't disconnect from the router, but I can't open any web site and all my internet applications (Skype, Dropbox, etc.) goes offline. The only way to go back online is to switch the wifi adapter off/on. All other devices (iPhone 4s, iPhone 5, iPad 1, iPad 2, Samsung Notebook) work fine, i.e. only new mac book has this issue. I've tried to change all possible settings on my router and I even replaced it with new one, but it didn't solve the problem... I use Buffalo WZR-HP-G300NH with DD-WRT v24SP2-MULTI (10/31/11) std firmware.
P.S.> This problem occurs after awakening from sleep, i.e. it connects to my router and I even can access other computer in LAN, but it can't see WAN.