Summarize this article:

Make sure that your modem is correctly connected to an outlet and that no wires are loose. Ensure that all wireless settings and connections are set to receive the wireless signal. Make sure you did not accidentally activate "airport mode" or switch to another internet network. Turn off your modem, wireless router and computer. Restart everything. In most cases, this will solve your internet problems. If you have been unable to solve your internet problems on your own, it's time to bring in a professional.

Summary:
Check all of the connections to ensure no wires were accidentally unplugged or loosened. Check your computer. Reboot everything. Contact Time Warner or Professional.