At the beginning of the summer my MacBook Air stopped connecting to the Internet. It would appear to be connected with 4 bars, but when I try to load a webpage, it would stall for a few minutes then display the "Safari can't open the page" message. I have tried EVERYTHING! I've trawled through multiple troubleshooting threads on MacRumors and Apple Support but nothing seems to work. I've tried deleting the network and re-adding it. I've tried renewing the DHCP lease. I've checked for proxies and firewalls. I've tried to access the internet through another application ("$ping http://www.google.com" returns "Unknown host"). I've tried resetting my router. What's weird is that iStat Menus says that the task SystemUIServer is occasionally uploading and downloading a few kilobytes. Also, I can access my router's settings page (192.168.1.1). I can access the internet from other devices fine, so I'm sure the problem is within the computer. However I have not tried accessing another network with the computer. Anyway, I would really like some help here, as I'm completely dumbfounded.