A few days ago i installed Kubuntu 10.04 In my wife's notebook, everything went wonderfully for a few days, until yesterday, for no apparent reason when starting the system we were left without a Wi-Fi connection, when looking at the classic network connection icon, the message was read "Network manager disabled" I tried to connect it using a network cable and there was no case either.
From another pc we did the research 
and we came up with a solution that revived Knetworkmanager and gave us the long-awaited internet connection 😉 we typed the following in a terminal:
sudo service network-manager stop cd / var / lib / NetworkManager / sudo rm NetworkManager.state sudo service network-manager start
Seen Kubuntu-is
Excellent!. I recently ran into that little problem and did not know the solution, what I did was download the Wicd network manager and its dependencies from another computer and install it on my laptop, but without a doubt this is much easier, thanks.
A greeting.
I am glad that it has helped you, the issue is that after getting Knetworkmanager to work, Wicd would have to be installed, because the problem will continue to appear, it is more recently I had to do the same procedure because I had the same problem, so tomorrow I will see if I install Wicd on that machine.
regards
The same thing happened to me several times with Kubuntu and because I did not have another computer to download or know this solution because I reinstalled many others. Luckily it happened after a few days and did not make much trouble. And yes, my solution was to install Wicd and without problems in more than a month. For me it will be a ritual of each installation. Also, I like that it has more options.
hehe it happened to me a long time ago that happens when the system is suddenly turned off or when it is suspended and turned off before returning from the suspension, I solved it by suspending it and returning it from the suspension, there are times that after suspending it and returning from the suspension you have to reboot and voila XD
Thanks for the input. I ran into that problem after trying to suspend the notebook and it failed. With this I could solve it.
regards
Thanks very much buddy. Such a simple solution that I had not been able to do. As others comment, I installed Wicd and made as many attempts installing and reinstalling packages. Anyway, the Ubuntu guys have to get their hands on here. Thank you very much again!
And I would like to add that it is with version 15.04 but it has also happened to me in previous versions.