MacBook Pro Retina 13″ not connecting to some Wifi networks

Try using iStumbler to detect and identify neighboring and overlapping wireless access points (WAPs). It's likely an interference issue that can be solved with vigilance. You need to find out what channels your neighbor's WAPs are using, and then switch your router to use the least crowded channel you can find.

Ideally you want to use channels 1, 6, or 11. These are the channels that have the most leeway when it comes to other channels interfering with their signal. Wifi devices operating on a particular channel can interfere with other devices operating on channels up to 5 steps away. The amount of interference grows logarithmically with signal strength and channel proximity.

For example, if you are using channel 1 and your nearest neighboring wireless network is also using channel 1, you are receiving a large amount of interference. If you are on 1 and the other network is on 6, the interference is negligible. However, if you are on channel 1 and your neighbor is using channel 3, you are likely still on the receiving end of a huge amount of interference depending on their WAPs signal strength.

iStumbler will give you information about the signal strengths emanating from the other interfering WAPs, and from there you can infer the best channel to use. You may need to periodically perform the same task as your neighbors change their wifi channels.

I had a similar problem.

In my case when I pulled down the airport icon it saw the connection, but would then not connect. Along the way to not connecting it would ask me to enter my password. Even after entering the proper password it would not connect.

I finally solved the problem by going in to /Application/Utilities/Keychain Access.app and deleting my home wifi's stored password.

The next time I connected - it asked for the password and from that point on it has connected just fine.