اینجا رو نگاه کن فکر کنم مشکلت رو حل میکنه
http://www.thebitguru.com/blog/view/328-%22device%20not%20managed%22%20in%20Ubuntu%20Karmic%209.10
1. Edit /etc/NetworkManager/nm-system-settings.conf and set managed=true
Specifically change the 'managed’ under ifupdown…
[ifupdown]
managed=false
...to true.
[ifupdown]
managed=true
2. Restart networking and network-manager services.
You can always restart the computer, but where is the fun in that
To get things to work without restarting, run the following commands.
sudo /etc/init.d/network-manager restart
sudo /etc/init.d/networking restart