I have installed Ubuntu 13.04 on my Lenovo-B-480 machine recently. I am not able to connect to wireless networks. Its detecting all the networks available, allowing me to type in the password but not enabling "Connect" button. Looking forward for any useful suggestion.
If the connect button is greyed out, your passphrase does not match the expected encryption standard.
For instance: WPA/2 passworts need to be between 8 and 64 Characters. If you have less characters in your passphrase, the connection Button will not activate.
It may happen that ubuntu does not correctly recognize your routers encryption. In this rare case you should edit your connections security to what your router is set to under Connections -> Wireless -> edit "Your connection" -> Security