Spend a long time to search WiFi and cannot join it automatically

Notebook: MacBook Air (2010)

OS: MacOS X 10.8.2

After upgrade to MacOS X 10.8.2, my MBA spent 10mins (sometime even more) to search WiFi everytime. But the strange is, the WiFi list on the top bar is empty and still searching (picture 1), but it has already found some WiFi networks on the network preference dialog box (picture 2). And even I have added my WiFi to the primary network list, my MBA didn't join it automatically.

BTW, my WiFi is OK , because my iPhone and iPad can find it very quick and join it automatically.

i'm not good at English, but i think you can get it:)

in the mean time,