Network Manager fails to connect to wifi, and displays a "connection deactivated" message every 5 seconds

[Dima Ryazanov]

I've connected to the same wifi network lots of times before, and I currently have other devices connected, so it's not a problem with the network. For whatever reason, Network Manager won't connect anymore, and keeps displaying "connection deactivated" messages, even though the connection never activated in the first place.

I tried disabling wifi and rebooting - but it didn't make a difference.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: network-manager 0.9.8.8-0ubuntu7
ProcVersionSignature: Ubuntu 3.13.0-29.53-generic 3.13.11.2
Uname: Linux 3.13.0-29-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.2
Architecture: amd64
CurrentDesktop: KDE
Date: Sat Jun 7 15:30:47 2014
EcryptfsInUse: Yes
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
InstallationDate: Installed on 2013-04-05 (428 days ago)
InstallationMedia: Kubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.1)
IpRoute:
 default via 192.168.1.1 dev wlan0 proto static
 192.168.1.0/24 dev wlan0 proto kernel scope link src 192.168.1.34 metric 9
SourcePackage: network-manager
UpgradeStatus: Upgraded to trusty on 2014-05-14 (24 days ago)
nmcli-dev:
 DEVICE TYPE STATE DBUS-PATH
 wlan0 802-11-wireless connected /org/freedesktop/NetworkManager/Devices/0
nmcli-nm:
 RUNNING VERSION STATE NET-ENABLED WIFI-HARDWARE WIFI WWAN-HARDWARE WWAN
 running 0.9.8.8 connected enabled enabled enabled enabled disabled