Very sporadic Wi-Fi Issue with Lion (Connection Timeout)
OK, lets try to Manually connect to your WiFi.

Use following in your Terminal app (located in the utility folder).

Turn On (skip this if it is on already)

networksetup -setairportpower en0 on


Find (skip this if you know the WiFi name and the passowrd)

/System/Library/PrivateFrameworks/Apple80211.framework/Versions/A/Resources/airport scan


Connect

networksetup -setairportnetwork en0 WIFI_SSID_I_WANT_TO_JOIN WIFI_PASSWORD


Just replace the "WIFI_SSID_I_WANT_TO_JOIN" with your WiFi name