Make sure you know your network passkey as you will need to re-enter it.
- Go to your main hard drive (usually Macintosh HD).
- Go to Library -> Preferences -> SystemConfiguration
- Delete the following files:
- com.apple.airport.preferences.plist
- com.apple.network.identification.plist
- NetworkInterfaces.plist
- preferences.plist
- Restart the computer. You will need to set up your wireless connection again including the passkey.