Try this; Unplug your router from cable modem and PC. Reset your cable modem and plug it straight into your PC. Then, wait and see if you get an IP. If you Don't, go to Start>Run>type "CMD", hit enter. when in the Command Prompt, type ipconfig /release, then type ipconfig /renew. You should get an IP then, and be able to get out to the internet. If you can, its a problem with your router (Do the factory reset, and set it back up.) If you can't get out to the internet, its a problem with your modem or cable company.
Hopefully that helps.