I think you need to install gnome-system-tools

apt-get install gnome-system-tools

or install using synaptic

It still does not work. It keeps say failed to fetch.

You need to have a Ubuntu CD-ROM. In Synaptic's options, choose the CD as the source of the file. Then after you have done that you can reinstall network manager through Synaptic.

See the section Configure Synaptic [url]http://www.watchingthenet.com/ubuntu-guide-for-windows-users-managing-packages-with-synaptic-and-apt-part-1.html[/url]

Also to backup your system in the future, see
[url]http://www.pubbs.net/ubuntu/200908/246/[/url]

I think there is no need to reinstall it . just use command :sudo pppoeconf to access to internet.

[quote name="Alaa Elian"]I have faced the same situation with my notebook, even worse it was a wireless connection which didn't work after uninstalling the network-manager on ubuntu 9.10. the solution was simply by doing the interface setup manually by editing two configuration files, the first was /etc/network/interfaces for setting the ip address, netmask, gateway, etc..., the second was /etc/wpa_supplicant/wpa_spplicant.conf for setting WPA key. Then I reinstalled the network-manager form the online repository.[/quote]

I mus try this, I have been using pppoeconf and Mint 8 to see if this intentional networkManager applet; which is broken!, because Ubuntu and Mr' Google are building a 55 chevy. I wonder if a fresh install of Ubuntu 10.04 has this fix?