Unable connect to WL500GD

Last week my ASUS WL500G Deluxe start to strike. A strange thing happend. He works well than he stop working. I unpugged the cord and put it back after a while it blinks as it normal but than shut down himself. I unpluged cord several times but it doesn't work. I pull out adapter for while than I plugged it back and it works for 20 secs until the ASUS try to start AIR connection. I try to upgrade (downgrade) fw but it won't work. I could ping router on IP 192.168.1.1 it gives me a fast response but I'm unable to connect router through the browser and set it up also is impossible to reset router with pluging out/in cord always has to be done with pulling out adapter. Without holding reset button works until the AIR LED strarts light than everything lights off aned router is dead.

First thing to check is the power supply.

Try another with the same specs.