ASUS WL-500gP V2 is a great router. One of good things is you can always unbrick it.
To unbrick it. unplug it, hold on the "restore" button, plug power, and wait for 5 seconds, the power LED should go into slow blinking. This shows that the box is in recovery mode.
Connect a PC to a LAN port, and make sure you disable all other network connections on the PC you are using to flash. This is the key!!
Set you PC Ethernet IP to 192.168.1.5/255.255.255.0. You will NOT be able to ping 192.168.1.1. That is OKAY.
Now fire up the ASUS Firmware Restoration utility (came with your box in the CD or downloadable from ASUS website in Utilties), and load the firmware.
Regardless whether your firmware is good or bad, you can always use this method to reflash the box.
DD-WRT sets the NVRAM password. I had to restore the firmware to ASUS firmware and press RESTORE button for more than 10 seconds, and reboot to erase the NVRAM password. Then I reflash my box to tomato firware.