Finally getting back to you w/ results of your suggestion after returning home. I was still troubleshooting the wireless issue, which popped up after installing updates, and checking results at the local library where there is WiFi.
Your suggestions to
sudo service network-manager start
did indeed stop "Network Manager not running" contextual menu while pointing to the NM applet on the task panel. But then, the "wireless connection" still did not list available networks, but stated "device not managed." Grrr...
Terminal said NM was running and listed job #, but nothing listed with the panel applet. To add insult to injury, after following instructions to make the terminal command permanent in gksudo pluma /etc/rc.local, the NM applet in the task panel disappeared altogether!
I was tempted to remove NM, and install wicd, but eventually found solution(s) on ubuntu forums:
First, reinstalled a new Network Manager (don't think I bothered to purge first); in terminal:
sudo apt-get install --reinstall network-manager network-manager-gnome
A) Then, in terminal:
sudo pluma /etc/NetworkManager/NetworkManager.conf
Change managed=false to managed=true.
B) Next, in terminal:
sudo pluma /etc/network/interfaces
Remove everything except:
iface lo inet loopback
(One might want to save content before removing.)
Reboot. Applet reappears on task panel! Be sure to right-click applet and check "Enable Networking" and "Enable Wireless." I also deleted all other accounts in "Edit Connections" though not sure this step was necessary. In Network Manager, I checked "Enable roaming mode" for wireless.
Network Manager is working fine now, and the computer is working more efficiently than ever.
For example, bootup no longer hangs on "Waiting for network configuration" & "Waiting up to 60 more seconds or network configuration."* Maybe the fixes enabled other updates to finally work.
Useful links for a more global understanding about "Device not managed" issue:
Hopefully this information helps others with similar update issues.
[* Tangent: Getting hung on boot messages "Waiting for network configurations" etc, can also be fixed this way:
sudo pluma /etc/init/failsafe.conf
>>>Add # (comment out) before every sleep command. There are four sleep commands. I did not have to do this after fixing Network Manager per above. Not sure why.]