MacBook Continuously "Locating networks"

I have a G5 iMac and an Intel MacBook running wirelessly via Time Capsule to a DSL connection. Recently I have noticed a significant decrease in performance over the internet on my MacBook only. My wireless signal is strong, but when I click on the icon, the Airport status toggles between 'On' and 'Locating Networks' every 10-seconds.

I set both computer side-by-side and cannot find any differences in the network preferences. So I'm seriously confused.

Any ideas...