I am running Ubuntu Gnome 14.04LTS and I can leave my desktop on for about 2 hours before the desktop stops responding. I can move the mouse on the screen, if there was music playing before, I can keep listening to it, and I can get into my system using SSH. All of the windows, however, freeze and the activities menu doesn't even respond. This happened after I updated my kernel/driver stack a couple of days ago (probably sunday-ish).
I can give any other info you need and do whatever additional steps are required.
[EDIT] I am using the open source drivers.
Attached as "crash.txt" the crash data that I receive when it crashes.
ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: xorg 1:7.7+1ubuntu8.1
ProcVersionSignature: Ubuntu 3.13.0-49.83-generic 3.13.11-ckt17
Uname: Linux 3.13.0-49-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.9
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: None
CurrentDesktop: GNOME
Date: Thu Apr 16 16:58:03 2015
DistUpgraded: Fresh install
DistroCodename: trusty
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes
GraphicsCard:
Advanced Micro Devices, Inc. [AMD/ATI] Curacao XT [Radeon R9 270X] [1002:6810] (prog-if 00 [VGA controller])
Subsystem: XFX Pine Group Inc. Device [1682:9275]
InstallationDate: Installed on 2015-04-15 (1 days ago)
InstallationMedia: Ubuntu-GNOME 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
MachineType: Gigabyte Technology Co., Ltd. To be filled by O.E.M.
ProcEnviron:
TERM=xterm
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-49-generic.efi.signed root=UUID=4451d4be-fc22-4f81-85c6-e2b684d6907a ro quiet splash vt.handoff=7
SourcePackage: xorg
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/06/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: F5
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: 970A-D3P
dmi.board.vendor: Gigabyte Technology Co., Ltd.
dmi.board.version: x.x
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: Gigabyte Technology Co., Ltd.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrF5:bd08/06/2013:svnGigabyteTechnologyCo.,Ltd.:pnTobefilledbyO.E.M.:pvrTobefilledbyO.E.M.:rvnGigabyteTechnologyCo.,Ltd.:rn970A-D3P:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: To be filled by O.E.M.
dmi.product.version: To be filled by O.E.M.
dmi.sys.vendor: Gigabyte Technology Co., Ltd.
version.compiz: compiz N/A
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.56-1~ubuntu2
version.libgl1-mesa-dri: libgl1-mesa-dri 10.1.3-0ubuntu0.4
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 10.1.3-0ubuntu0.4
version.xserver-xorg-core: xserver-xorg-core 2:1.15.1-0ubuntu2.7
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 2:2.99.910-0ubuntu1.4
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.10-1ubuntu2
xserver.bootTime: Thu Apr 16 16:34:46 2015
xserver.configfile: default
xserver.devices:
input Power Button KEYBOARD, id 6
input Power Button KEYBOARD, id 7
input MOSART Semi. 2.4G RF Keyboard & Mouse KEYBOARD, id 8
input MOSART Semi. 2.4G RF Keyboard & Mouse KEYBOARD, id 9
input Solid State System Co.,Ltd. USB headset BSF KEYBOARD, id 10
xserver.errors:
xserver.logfile: /var/log/Xorg.0.log
xserver.version: 2:1.15.1-0ubuntu2.7
xserver.video_driver: radeon
Installing the xorg-edgers stack