I've had the same problem but solved it.
My Windows 7 laptop could access to the internet through my D-link router in about several days, then it suddenly said that it had no internet access although it had the connection with the router and the signal strength was excellent. I tried all of the solutions above and from other sources but they all didn't help.
Then I got notice of the Wireless LAN adapter Wireless Network Connection 2 which I have not seen before. My wireless LAN adapter is named Wireless Network Connection and it is functioning. Then I tried to disable the Wireless LAN adapter Wireless Network Connection 2 and it just... worked!
I do not know if this is a long-term solution to this problem because the Wireless LAN adapter Wireless Network Connection 2 is still there although disabled.