I'm currently working in 13.04. The network manager indicates that the WIFI is always connected. However, the Internet connection only last a few seconds and then it disconnects. The problem only exist when I want to connect to a WPA2-Enterprise protected network. There is not problem if I connect another unprotected network.
I have tried the nohwcrypt=1 method, but it does not help.
What can be the problem? Let me know if you need any further information.