I have changed managed to true in NetworkManager.conf, commented out the "iface eth0 inet dhcp" line and rebooted, but the problem stays.
If I uncomment again the "iface eth0 inet dhcp" line then eth0 gets connected and the "fixed line connected" appears. The network manager applet indicates that eth0 is under ifup control.
Thanks for the hint.
I have changed managed to true in NetworkManager. conf, commented out the "iface eth0 inet dhcp" line and rebooted, but the problem stays.
If I uncomment again the "iface eth0 inet dhcp" line then eth0 gets connected and the "fixed line connected" appears. The network manager applet indicates that eth0 is under ifup control.