1024x768 is the highest resolution available on Toshiba Satellite A505-S6960

After updates on my Raring Ringtail install a couple days ago, Ubuntu no longer displays at my laptop's real resolution of 1366x768 anymore. It displays instead in a square 1024x768 box in the center of my screen instead, with black rectangles on either side of the screen. Figuring the problem might just have been a buggy update, I made a LiveUSB with a fresh ISO and can confirm the bug is there in the live session, too.

Note that GRUB and Plymouth still display suing the whole display at full resolution. The bug is visible in the login screen and the desktop.

I have not overwritten my current Raring install yet, so I can go back to that for additional debugging work if need be. I'm filing this bug report from within the LiveUSB session using xdiagnose.

This is a pretty nasty regression and I'd like the sides of my screen back, please. :)

A screenshot of the problem on my HDD install is available here: https://plus.google.com/109509247327281928543/posts/EeGWaDrfQij

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: xorg 1:7.7+1ubuntu4
ProcVersionSignature: Ubuntu 3.8.0-13.22-generic 3.8.3
Uname: Linux 3.8.0-13-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.9.1-0ubuntu1
Architecture: amd64
CasperVersion: 1.330
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
Date: Wed Mar 20 01:01:23 2013
DistUpgraded: Fresh install
DistroCodename: raring
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes, if not too technical
GraphicsCard:
 Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller [8086:2a42] (rev 07) (prog-if 00 [VGA controller])
   Subsystem: Toshiba America Info Systems Device [1179:ff10]
   Subsystem: Toshiba America Info Systems Device [1179:ff10]
LiveMediaBuild: Ubuntu 13.04 "Raring Ringtail" - Alpha amd64 (20130318)
MachineType: TOSHIBA Satellite A505
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: noprompt cdrom-detect/try-usb=true file=/cdrom/preseed/username.seed boot=casper initrd=/casper/initrd.lz quiet splash -- maybe-ubiquity
SourcePackage: xorg
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/25/2010
dmi.bios.vendor: INSYDE
dmi.bios.version: 1.80
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: Portable PC
dmi.board.vendor: TOSHIBA
dmi.board.version: Base Board Version
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: Chassis Manufacturer
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnINSYDE:bvr1.80:bd05/25/2010:svnTOSHIBA:pnSatelliteA505:pvrPSAP0U-007007:rvnTOSHIBA:rnPortablePC:rvrBaseBoardVersion:cvnChassisManufacturer:ct10:cvrChassisVersion:
dmi.product.name: Satellite A505
dmi.product.version: PSAP0U-007007
dmi.sys.vendor: TOSHIBA
version.compiz: compiz 1:0.9.9~daily13.03.08-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.42-0ubuntu2
version.libgl1-mesa-dri: libgl1-mesa-dri 9.0.3-0ubuntu1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 9.0.3-0ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.13.3-0ubuntu2b1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.7.3-0ubuntu2b2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.1.0-0ubuntu1b1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.21.4-0ubuntu1b1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.6-0ubuntu3b1
xserver.bootTime: Tue Mar 19 20:57:56 2013
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.version: 2:1.13.3-0ubuntu2b1
xserver.video_driver: intel