Why does snow leopard take so long to subscribe to wifi?

Until Snow Leopard, my Macs easily logged on to my Aiport wifi network, more or less instantly on awakening from sleep. Since upgrading to Snow Leopard, log on always takes 5 or more seconds (it appears to be searching for networks—there is only one available in my rural home.) Sometimes, it fails to log on at all and I have to find my one and only network from the menu bar. This is not fatal but it is annoying. What has changed with OS 10.6?