Just thinking about some more stuff that we can look at/try. Not in any order, just off the top of my head.
• If a ports light is lit, a link has been established to the connected device. If a LAN port is connected to a 100 Mbps device, verify that the ports light is green. If the port is 10 Mbps, the light will be amber. What color is the MacBook port?
• If the light is NOT GREEN ... What is the speed that the Macbook Airport set to set to? b/g/n ?
• Reboot the Router.
• What does Network Utility show as your wireless speed?
• If Bluetooth is on, turn it off.
• Use WPA2 as your encryption mode (All Devices).
• Try changing the channel that your wireless is on (Try Channel 11 as a starting point in the router and the MacBook; then 2, then 6.) You can use this »www.istumbler.net/
to check your wireless single's strength. Use the channel that has the highest single. You can also see nearby networks that might be interfering with you.
• How far away are you from the router? Walls & stuff? Bring the Macbook close to the router. Any improvement?
• Try resetting your the PRAM and NVRAM »support.apple.com/kb/ht1379
• Try resetting the System Management Controller (SMC)
"You can observe a lot by watching". Yogi Berra