Here is a puzzling problem I currently have. i have two iMacs, one notebook, two iPhones and one Ipad, and have no problem connecting to the Internet on any of them but one: iMac 24" (white). All others have 20-30Mbs download and 5-6Mbs upload speeds. They are all using wi-fi. Can not detect any difference in settings on the 24" one, nor diagnostic returns any malfunctioning, and yet the speed is either non-existing or real slow (it starts measuring the speed at speedtest.net, reaches 0.02 - though it should be 20 - and then freezes there). I tried emptying the cache and restarting. Any ideas?