surefire quickest solution, Power down the router, hold in the little reset button with a pen while reconnecting the power. This puts the box back to factory defaults. Then connect your PC to it using a network cable and type Http://192.168.0.1 in your browser and log in with username admin and password admin.
This will without fail let you into the router settings. Then set it up as requred taking time to document everything you do to prevent further issues like this.
Skidilliplop said:All linksys boxes do. The method is without fail only within this thread, not globally.
The WAG54GS uses 192.168.1.1.