Problems with Wireless since upgrade to 14.04

[Graham Cox]

My laptop is a Toshiba Satellite L750, which has a Qualcomm Atheros AR9285 Wireless Network Adapter in it. When I was running 13.10 it all worked perfectly fine, but ever since I upgraded to 14.04 - literally, ever since the reboot after installing it - it has been problematic. The curious thing is though, it is only problematic connecting to the home Wi-fi and not to other wi-fi services. Specifically, I am now connected to my Android phone acting as a wi-fi hotspot so that I can post this question, and it works perfectly. This laptop is the only device in the house that has trouble connecting to this wi-fi router as well - our tablets and phones all connect perfectly well, as does my partners Windows laptop. Also, the connection to the home wi-fi will sometimes work perfectly well and other times just not work at all, and the only thing I've been able to find that will make any difference at all is to just wait and try again later. If it doesn't work now - which it doesn't - then in an hours time it might work perfectly well as if nothing was wrong, but if I then shut the lid and come back it will stop working again...

Information:

$ lspci | grep -Ei wireless
02:00.0 Network controller: Qualcomm Atheros AR9285 Wireless Network Adapter (PCI-Express) (rev 01)
$ lshw
.....
           *-network
                description: Wireless interface
                product: AR9285 Wireless Network Adapter (PCI-Express)
                vendor: Qualcomm Atheros
                physical id: 0
                bus info: pci@0000:02:00.0
                logical name: wlan0
                version: 01
                serial: e0:ca:94:98:ec:00
                width: 64 bits
                clock: 33MHz
                capabilities: bus_master cap_list ethernet physical wireless
                configuration: broadcast=yes driver=ath9k driverversion=3.13.0-24-generic firmware=N/A ip=192.168.43.212 latency=0 link=yes multicast=yes wireless=IEEE 802.11bgn
                resources: irq:17 memory:c0500000-c050ffff
.....
$ uname -a
Linux daedalus 3.13.0-24-generic #47-Ubuntu SMP Fri May 2 23:30:00 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

A section of /var/log/syslog from when it tries to connect to the home wi-fi is pasted at http://pastebin.com/dPHEa7p8 too - as it was rather too long to stick in here...

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: network-manager 0.9.8.8-0ubuntu7
ProcVersionSignature: Ubuntu 3.13.0-24.47-generic 3.13.9
Uname: Linux 3.13.0-24-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.1
Architecture: amd64
CurrentDesktop: Unity
Date: Mon May 26 21:56:00 2014
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
InstallationDate: Installed on 2013-12-14 (162 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
IpRoute:
 default via 192.168.43.1 dev wlan0 proto static
 192.168.43.0/24 dev wlan0 proto kernel scope link src 192.168.43.212 metric 9
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
 WimaxEnabled=true
ProcEnviron:
 LANGUAGE=en_GB:en
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: network-manager
UpgradeStatus: Upgraded to trusty on 2014-05-17 (9 days ago)
nmcli-dev:
 DEVICE TYPE STATE DBUS-PATH
 eth0 802-3-ethernet unavailable /org/freedesktop/NetworkManager/Devices/1
 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

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.