MacBook lost wireless connection
I had the same problem (strangely, on the same day). My MacBook Pro would see and connect to the router but not be allowed past it, to the internet. Other devices had no such trouble, and resets of both the laptop and the router had no effect.

In my case, I had set a certain maximum number of DHCP clients on my router, and all the entries had been taken up. Raising this number by one allowed my MacBook to connect.