I have a Mid-2011 13" Macbook Air running OS X 10.9.2 (the latest version). When I wake my Mac from sleep, sometimes, the Wifi will fail to find my network. The network icon will display the connecting symbol. The only way to stop that is to turn off wifi and turn it back on, where it will reconnect almost instantly.
A video I made showing my problem: http://www.youtube.com/watch?v=EtwPg9ff4WE&feature=youtu.be