Did you ever resolve this problem? I have a new MBA and am having a similar issue. For known networks (i.e. the password is in the keychain because I joined them before this bug appeared) I get the "connection timeout occurred" message instantly, but I join the network successfully. For unknown networks I enter the password and instantly get the "Connection failed" message (although the network is joined). However, because the MBA *thinks* the connection has failed it doesn't store the password in the keychain, meaning I have to enter it every time I subsequently connect.