I have had the same problem with my MacBook Air from new, bought it 6 months ago, it is constantly searching for Wifi, finds it, drops it, continues search, but it has worked most of the time. From yesterday I changed something because it lost the signal altogether, all the boxes were 'fail'. Now this morning it has a signal again, but the wifi icon has disappeared, only Bluetooth, no connection, even though I am able to do anything on line. Can anyone help me with this please?