| I've had two routers die on me.  Well, I do abuse them by putting different (hacker-friendly) firmware on them so I can do what I want to do with them (turn them into powerful wireless cards).
 I would suggest getting a packet sniffer and seeing what traffic is on your network.  Ethereal is one I've used before.  Apple has one, but I haven't used it yet.
 
 Was it connected to the cable modem?  Would there be traffic from the WAN network pinging your router relentlessly?
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