解決方式如下：
Fix nm-applet can't execute error
1.修改/etc/dbus-1/system.d/NetworkManager.conf 和 /etc/dbus-1/system.d/nm-applet.conf
將下列字，如果为deny，改allow
<policy context=default>
<allow own="org.freedesktop.NetworkManager"/>
<allow send_destination="org.freedesktop.NetworkManager"/>
<allow send_interface="org.freedesktop.NetworkManager"/>
</policy>
2.重新启动 dbus
sudo /etc/init.d/dbus restart
Fix nm-applet "No connection defined" error
3.停止 NetworkManager
sudo /etc/init.d/NetworkManager stop
4.刪除 /etc/network/interfaces 或是更名(rename)
sudo rm /etc/network/interfaces
5.重新启动 NetworkManager
sudo /etc/init.d/NetworkManager start
6.执行nm-applet
解决Ubuntu控制面板network-manager图标现实问题：http://www.linuxdiyf.com/linux/9690.html
Ubuntu 10.10误删network-manager的解决：http://www.linuxdiyf.com/linux/9001.html