Before you go into your Mac's settings, TURN THE ROUTER/MODEM OFF. Let it sit for AT LEAST TWO MINUTES (TIMED!!!). After that, turn it back on and then try to renew your Mac's DHCP address. This may not help, but it just might, and that would save you a lot of trouble.
ALWAYS TRY A RESTART OF YOUR ENTIRE NETWORK SETUP BEFORE GOOFING AROUND WITH ANY SETTINGS. That's "Glenn's First Law of Network Troubleshooting" and you (everyone) should remember it all the time.