Network Setting problem in Ubuntu 9.04

I believe many people have seen "wired device not managed" in Ubuntu network-manager in gnome.
And even if you know how to set a /etc/network/interface config file to manually start networking, you get no nothing after reboot system.
A simple way to solve this problem is set
[ifupdown] managed=true
in /etc/NetworkManager/nm-system-settings.conf to resolved the issue.