Just reset the router using the Pinhole on the back to get it back to factory defaults. That will get the Wi-Fi back since it resets the router back to the state in which you received it originally. From there, you'll want to try enabling UPnP in the router, and then disabling the IGMP proxy within the router. A quick search of this forum should be able to find the links to get to those settings in the router, but if you could tell us the make and model, along with revision of your router that would be appreciated.
You're welcome. Enjoy!
Also a fun fact: If you have an ActionTec MI424WR Rev. F or newer, make sure it's set for WPA2 encryption (though anything lesser I would set it to there anyways for security sake). You'll get some higher speeds on the Wi-Fi if it's currently set to WPA or WEP only.