In my iPhone4 Settings where I'm suppose to turn Wi-Fi on or off, it it just grey & says 'No Wi-Fi'. I have reset network settings & restored phone & re-synced everything, but still have this problem. Does anyone know how to fix this?
See this Apple support page: http://support.apple.com/kb/TS1559
There are also reports that this might be caused by a burnt out wifi chip or an internal wifi antenna connector gone bad, either of which indicates that a trip to a Genius bar may be in order.