Yesterday morning, I lost my internet for a while. My network icon said that there was internet available and my ISP said my modem was getting a proper signal.

I bypassed my router and everything was ok, but that's not a viable workaround as I have 2 PCs, my Xbox, my work laptop, the wife's Kindle and 2 iPods that all need Wi-Fi or a wired connection.

I pinged a network guy at work and he suggested cloning my PCs MAC on the router. I did that, and everything returned to normal.

As everything was fine up until yesterday, can someone explain why I would have to clone my MAC? What does that accomplish between my private network and Cox's? Is Cox doing something shady that would require me, out of the blue one day, to clone my MAC?

MAC cloning, which is your machine access code, basically is like creating a second copy of the fingerprint of your hardware. Your router is the only MAC an ISP sees because the rest of your MACs (your computers, your kindle, etc) are hidden behind the router. If you signed up for internet and did not have the router when you originally did, it can cause problems sometimes cuz its lookin for the MAC for your PC and when it gets the router it gets pissed. Cloning it fools the ISP into thinking your router is actually your PC.

Ahh, ok. I think I DID only have just my PC when I got service. But, what would account for, literally, YEARS passing before this caught up to me? Did they do a random audit or something?

your modem stores a data base of MACs from all of your componets, 99% of the modems out there are locked down so that you can't restrict MACS like on personal router.( for this reason I am not quite sure why) However, the modems are cheap POS and they have a tendacy to fail.( like my motorola modem that Cablevision only permits) I had to call the ISP have them go into my modem and have them reset it. Some modems look for updates from the parent server that gets pushed down to it. This can cause problems too. Either way try having them reset it, all you might be able to do it soft and hard reboot. but they can edit details for you. Not much you can do since they have you by teh balls on this situation. If your problem still exists, tell them it broke you demand a replacement, unfornately you'll have to go to thier shop to swap them out.