My macbook pro stopped detecting my wireless router (NetGear DG834G)
The first step would be to open the folder /System/Library/CoreServices and run Wireless Diagnostics to get to the Utilities window (⌘+2) and run a wireless scan to check on your base station and whether the antenna on the Mac is picking up signals similar to your other devices.



You'll want to inspect your base station (match the BSSID with the Mac address for your wireless router) and ensure that your signal to noise ratio is better than all of the ones I have shown. Ideally, your RSSI should be greater than -80 dBm: -90 dBm is bad, -60 dBm is OK, and your channel not within 2 of a neighboring station).

From there, you could select performance or run the actual diagnostics or see if perhaps you need to select a channel with less interference.



As you can see in this view, even with no wireless network connected, you can run the tool. Once you join your network, this performance view will help you getting connected. Once you are connected, you can monitor things here and lastly, use the Info button to see what alternate channels you might try to let your Mac work with your exact router and the competing devices that also interfere with each other.