My laptop with lubuntu 12.04 used to connect to the wifi. But after the router (Cisco E4200) was restarted I cannot connect anymore through wireless connection. (No problem using a cable.) The network is hidden and secured by WPA/WPA2 Personal, I am the only person having this problem, so I guess it's somewhere on my side. What could cause such a problem, how to diagnose it and finally how to fix it?