Reproduce steps:
1) Change account to guest by click guest account on the menu.
2) Change account to user again
3) Touchpad lost its function.
When the touchpad becomes malfunction, there are some messages in /var/log/Xorg.0.log
[ 282.908] (WW) synaptics: SynPS/2 Synaptics TouchPad: can't grab event device, errno=16
[ 282.940] [dix] couldn't enable device 11
[ 282.940] setversion 1.4 failed: Permission denied
ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: xserver-xorg-input-synaptics 1.7.4-0ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-41.69stella1-generic 3.13.11.10
Uname: Linux 3.13.0-41-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.2
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Dec 4 02:25:41 2014
DistUpgraded: Fresh install
DistributionChannelDescriptor:
# This is a distribution channel descriptor
# For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
canonical-oem-stella-neihu-trusty-amd64-20141125-0
DistroCodename: trusty
DistroVariant: ubuntu
InstallationDate: Installed on 2014-12-04 (0 days ago)
InstallationMedia: Ubuntu 14.04 "Trusty" - Build amd64 LIVE Binary 20141125-01:45
Lsusb:
Bus 001 Device 003: ID 0bda:5776 Realtek Semiconductor Corp.
Bus 001 Device 002: ID 8087:8000 Intel Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: Hewlett-Packard HP 15 Notebook PC
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-41-generic root=UUID=f7c1e040-6471-4e14-9e77-bb406b63fad3 ro quiet splash video.use_native_backlight=1 radeon.modeset=0 nouveau.modeset=0 vt.handoff=7
SourcePackage: xserver-xorg-input-synaptics
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 10/28/2014
dmi.bios.vendor: Insyde
dmi.bios.version: F.32
dmi.board.asset.tag: Type2 - Board Asset Tag
dmi.board.name: 2211
dmi.board.vendor: Hewlett-Packard
dmi.board.version: 86.45
dmi.chassis.asset.tag: Chassis Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: Hewlett-Packard
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnInsyde:bvrF.32:bd10/28/2014:svnHewlett-Packard:pnHP15NotebookPC:pvr097F120000005F00001620100:rvnHewlett-Packard:rn2211:rvr86.45:cvnHewlett-Packard:ct10:cvrChassisVersion:
dmi.product.name: HP 15 Notebook PC
dmi.product.version: 097F120000005F00001620100
dmi.sys.vendor: Hewlett-Packard
version.compiz: compiz 1:0.9.11.2+14.04.20140714-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.52-1
version.libgl1-mesa-dri: libgl1-mesa-dri 10.1.3-0ubuntu0.1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 10.1.3-0ubuntu0.1
version.xserver-xorg-core: xserver-xorg-core 2:1.15.1-0ubuntu2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.8.2-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.3.0-1ubuntu3.1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.910-0ubuntu1.1stella3
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.10-1ubuntu2
xserver.bootTime: Thu Dec 4 02:21:16 2014
xserver.configfile: default
xserver.errors:
xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:
product id 17900
vendor AUO
xserver.version: 2:1.15.1-0ubuntu2
Most propably, this should be reported against lightdm.