After some investigations I found that any program which alters the /etc/network/interfaces file deleting the "auto" command from a wireless interface messes up knetworkmanager. To workaround the problem just put back the "auto" command before the wireless interface name.
Example: auto eth0 iface eth0 inet dhcp wifi0 iface wifi0 inet dhcp Change it in auto eth0 iface eth0 inet dhcp auto wifi0 iface wifi0 inet dhcp -- knetworkmanager fails to find network devices https://launchpad.net/bugs/77557 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
