Is your laptop able to connect to other networks? If so, your router maybe at fault. Reset the router, if it still doesn't work, you may need a new router. If your laptop has issues connecting to other networks, the wifi radio in your laptop may need to be replaced.

If you're getting a limited or no connectivity message the primary reason for that is the network key that you're using isn't correct. It's possible that somebody change your security key. If that's the case I suggest call the router's manufacturer to get the right key or maybe there's a need for you to change the wireless channel of the router.