Did you install using 14.04.2 media? Then you're using the driver stack from 14.10. You could try using 'Option "AccelMethod" "uxa"' in xorg.conf (man intel), or update to vivid lts stack in trusty-proposed.
** Package changed: xorg (Ubuntu) => xserver-xorg-video-intel (Ubuntu) -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to xserver-xorg-video-intel in Ubuntu. https://bugs.launchpad.net/bugs/1472471 Title: XServer crash logs the user off randomly Status in xserver-xorg-video-intel package in Ubuntu: Incomplete Bug description: System: Ubuntu 14.04, running cinnamon, on a Dell M3800. The bug happens randomly and logs off the user, who loses everything in the current session. It happens mostly when a new window is openned, especially terminals (but not only). > cat /proc/version_signature Ubuntu 3.16.0-41.57~14.04.1-generic 3.16.7-ckt11 The same happens with the latest 3.16.0-43 kernel. Here's what I found in the Xorg.0.log.old file: [ 1063.253] (EE) Backtrace: [ 1063.254] (EE) 0: /usr/bin/X (xorg_backtrace+0x48) [0x7fe8e43aaed8] [ 1063.254] (EE) 1: /usr/bin/X (0x7fe8e4206000+0x1a8f19) [0x7fe8e43aef19] [ 1063.254] (EE) 2: /lib/x86_64-linux-gnu/libc.so.6 (0x7fe8e2385000+0x36d40) [0x7fe8e23bbd40] [ 1063.254] (EE) 3: /usr/lib/xorg/modules/drivers/intel_drv.so (0x7fe8de18b000+0x258f9) [0x7fe8de1b08f9] [ 1063.254] (EE) 4: /usr/lib/xorg/modules/drivers/intel_drv.so (0x7fe8de18b000+0x26d7c) [0x7fe8de1b1d7c] [ 1063.254] (EE) 5: /usr/lib/xorg/modules/drivers/intel_drv.so (0x7fe8de18b000+0xf4f4f) [0x7fe8de27ff4f] [ 1063.254] (EE) 6: /usr/bin/X (0x7fe8e4206000+0x1755bd) [0x7fe8e437b5bd] [ 1063.254] (EE) 7: /usr/bin/X (0x7fe8e4206000+0x176397) [0x7fe8e437c397] [ 1063.255] (EE) 8: /usr/bin/X (DRI2GetBuffersWithFormat+0x10) [0x7fe8e437c770] [ 1063.255] (EE) 9: /usr/bin/X (0x7fe8e4206000+0x178499) [0x7fe8e437e499] [ 1063.255] (EE) 10: /usr/bin/X (0x7fe8e4206000+0x5369e) [0x7fe8e425969e] [ 1063.255] (EE) 11: /usr/bin/X (0x7fe8e4206000+0x574ea) [0x7fe8e425d4ea] [ 1063.255] (EE) 12: /lib/x86_64-linux-gnu/libc.so.6 (__libc_start_main+0xf5) [0x7fe8e23a6ec5] [ 1063.255] (EE) 13: /usr/bin/X (0x7fe8e4206000+0x42a5e) [0x7fe8e4248a5e] [ 1063.255] (EE) [ 1063.255] (EE) Bus error at address 0x7fe890108000 --- ApportVersion: 2.14.1-0ubuntu3.11 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC1: csoler 7078 F.... pulseaudio /dev/snd/controlC0: csoler 7078 F.... pulseaudio DistroRelease: Ubuntu 14.04 HibernationDevice: RESUME=/dev/mapper/swap InstallationDate: Installed on 2015-06-18 (19 days ago) InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1) MachineType: Dell Inc. Dell Precision M3800 Package: linux (not installed) ProcFB: 0 inteldrmfb ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.16.0-41-generic root=UUID=ed58d38e-680c-4454-863d-9c8e4698082c ro quiet splash ProcVersionSignature: Ubuntu 3.16.0-41.57~14.04.1-generic 3.16.7-ckt11 PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: Home directory not accessible: Permission denied No PulseAudio daemon running, or not running as session daemon. RelatedPackageVersions: linux-restricted-modules-3.16.0-41-generic N/A linux-backports-modules-3.16.0-41-generic N/A linux-firmware 1.127.12 Tags: trusty Uname: Linux 3.16.0-41-generic x86_64 UpgradeStatus: No upgrade log present (probably fresh install) UserGroups: _MarkForUpload: True dmi.bios.date: 01/08/2015 dmi.bios.vendor: Dell Inc. dmi.bios.version: A09 dmi.board.name: Dell Precision M3800 dmi.board.vendor: Dell Inc. dmi.board.version: A09 dmi.chassis.type: 8 dmi.chassis.vendor: Dell Inc. dmi.chassis.version: Not Specified dmi.modalias: dmi:bvnDellInc.:bvrA09:bd01/08/2015:svnDellInc.:pnDellPrecisionM3800:pvrA09:rvnDellInc.:rnDellPrecisionM3800:rvrA09:cvnDellInc.:ct8:cvrNotSpecified: dmi.product.name: Dell Precision M3800 dmi.product.version: A09 dmi.sys.vendor: Dell Inc. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/1472471/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp