Connection problem in modem or router?

My setup is a cable modem (Comcast) and then a wireless-G router (Netgear). This has happened more than once: My internet connection goes out. I try power cycling the router, and it comes up saying it can't get an IP address from the modem. I try the "stand by" button on the modem. It... show more My setup is a cable modem (Comcast) and then a wireless-G router (Netgear).

This has happened more than once:

My internet connection goes out.
I try power cycling the router, and it comes up saying it can't get an IP address from the modem.
I try the "stand by" button on the modem. It doesn't fix the problem.
I have to actually unplug the modem, wait for it to re-connect, and then turn on the router.

At this point I have internet access back. But my computer's diagnostic still says "The wireless router/AP for your network is working, but your computer is not able to use an IP address to connect to the Internet."

Comcast says there's nothing wrong with their modem, blaming it all on the router.

What is the most likely cause for the connection loss? Is there any way to prove whether it's the modem or the router without replacing both?
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