If Network Manager reports that your ethernet (wired) connection is un-managed, 
or you don't see the Network Manager applet icon at all, there are two 
solutions possible detailed below. Feel free to choose any. 
    https://help.ubuntu.com/community/Lubuntu/Documentation/AlternateInstall

NetworkManager will only handle interfaces not declared in 
/etc/network/interfaces (see README file). 

technical details:
    http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=530024
    http://wiki.debian.org/NetworkManager