Comment 12 for bug 577678

Got this problem when building RAID array on 10.04.1....
No problem when creating and configuring the array with Live CD for AMD64: nm-applet present and correct, fully functioning.
To install Linux have to switch to ALTERNATE CD, in which I entered fixed-IP (I prefer not to use DHCP) via the CD's text-based interface. When all finished and finally booted, no nm-applet in Notification Area. Likewise" System > Preferences > Network Connections" reported that there was no known configuration for eth0. ifconfig, however, reported eth0 fully configured (with the values entered via the Alternate CD), and Firefox could access anything I wanted.
Removing and re-installing nm-applet didn't fix it, neither did removing and re-installing network-manager-gnome. Removing and re-installing the Notification Area and/or the Indicator Applet made no difference either. The final solution was quite simple, thus:
Edit /etc/network/interfaces to remove all but the lo configuration (as recommended by Enrico Sardi, above) then reboot. Nm-applet now re-appears in Notification are, and" System > preferences > Network Connections" now recognises and reports an eth0 configuration that has never been used. Configure eth0 via either nm-applet or "Sys > Pref > Net Conn" and all is well.
Conclusion: the IP-configuration mechanism on the Alternate CD interferes with (and possibly corrupts) the operation of network-manager-gnome, or similar. Perhaps the developers might like to investigate?