Mac does not autoconnect to wifi network

Make sure in System Preferences > Network > Airport > Advanced > Airport, that the "Remember any network this computer has joined" is checked and that "Disconnect from wireless networks when logging out" is unchecked.

 

My Macbook is doing exactly the same thing. Any WPA2 protected network, it won't auto-connect to it on wake (or boot up).

It connects for about 3-5 seconds, and then drops the connection and pops up the window saying "none of your preferred networks are available"... and there's my network in the list to click and connect to with no problems.

Any other advice from anyone would be appreciated... I've had this issue for about 4 months now and even Apple Geniuses can't solve it!!

 

I am having this problem with mac os lion with my macbook pro. it was working before i updated to lion. Iv tried changing every setting, deleting the networks, everything i can think of. any ideas ?