I've had nothing but bad luck with NetGear. But brand preferences aside, if you're getting a link light on the Netgear router for WAN/Internet when you plug the ethernet cable from the cable modem in, it's not likely to be the cable. With my old Netgear router, I occasionally had to do a hard reset of it and re-set all the options to get it working again. Instructions on doing such a reset should be in your manual, which you can get off NetGear's site if you no longer have it.
If connecting straight to the cable modem is getting you a connection, the problem is definitely in the Netgear router. I would try the hard reset, and if that doesn't work, double-check settings in the router to make sure it's getting its IP from the cable modem (DHCP = On/yes), as that is the simplest way to get addressing between the two working. Problems with routers are often ethereal and difficult to track down, let us know what you try and whether it works!