Lol
I had this happen for me, once I had to get a new modem because comcast is a snake forget face mcgee starfish monday
But then I fixed it for my newest one.
Here's what I did.
Unplugged all and plugged in as following- Cable cord into a splitter, one split into the TV, the other into my modem. My modem is connected the the router right next to it, which provides wifi for my ps3 and ethernet cable goes to my computer. I deleted my connection on my computer and set up a new network. Also, I had to restart the modem and router like 1000 times before the forgeter worked, but it did.
Lol that's not any help, but that's what I did.