Looking at my Asus WL-500W router I found a strange LED-count: After booting the PWR-LED and AIR-LED went off, all other LEDs on.

LED-count ASUS WL-500W with b0rked power adaptor

Reset does not help. During a reboot (with even stranger and never seen LED counts) not a single packet could be detected on ethernet.

Answer to the problem: The power supply sucks. Changed it and everything works like a charm.

Regular LED-count: ASUS WL-500W with new power supply

So anybody who finds a router doing strange things: Spend a thought about the power supply! Could save lots of debugging time and could save you from spending money for a new router while the problem could be fixed with a 10€ power adaptor.

Update

2010-04-28  -  In August 2009 I replaced the defect power supply by an identical one from a spare WL-500W. That one is now dead too – after less than eight Month. The open circuit voltage is around 1V (should be 5V). That’s really poor, Asus :-(

BTW: This seems to be a common problem: vip.asus.com > Forum > Wireless > WL-500W