It looks like nouveau is gpu hanging on boot for some reason. When you're setting nomodeset, it's disabling nouveau entirely so you're booting with vesa, which won't give the best graphics. Anyway, that's why it works in that case.
** Changed in: xserver-xorg-video-nouveau (Ubuntu) Importance: Undecided => Medium ** Changed in: xserver-xorg-video-nouveau (Ubuntu) Status: Confirmed => Triaged -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to xserver-xorg-video-nouveau in Ubuntu. https://bugs.launchpad.net/bugs/1098316 Title: Ubuntu crashes on graphical login Status in “xserver-xorg-video-nouveau” package in Ubuntu: Triaged Bug description: Ubuntu crashes on graphical login, unless I use boot option nomodeset or acpi=off lsb_release -rd Description: Ubuntu Raring Ringtail (development branch) Release: 13.04 jolo@conroe:~$ apt-cache policy xserver-xorg-video-nouveau xserver-xorg-video-nouveau: Installed: 1:1.0.6-0ubuntu1 Candidate: 1:1.0.6-0ubuntu1 Version table: *** 1:1.0.6-0ubuntu1 0 500 http://ftp.snt.utwente.nl/pub/os/linux/ubuntu/ raring/main amd64 Packages 100 /var/lib/dpkg/status [ 533.755903] nouveau [ PFIFO][0000:01:00.0] still angry after 101 spins, halt [ 612.341956] nouveau E[ DRM] GPU lockup - switching to software fbcon [ 616.284009] nouveau E[ 1152] failed to idle channel 0xcccc0001 [ 618.285327] nouveau E[ PFIFO][0000:01:00.0] channel 3 unload timeout [ 621.284006] nouveau E[ 1152] failed to idle channel 0xcccc0000 ProblemType: Bug DistroRelease: Ubuntu 13.04 Package: xserver-xorg-video-nouveau 1:1.0.6-0ubuntu1 ProcVersionSignature: Ubuntu 3.7.0-7.15-generic 3.7.0 Uname: Linux 3.7.0-7-generic x86_64 .tmp.unity.support.test.1: ApportVersion: 2.8-0ubuntu1 Architecture: amd64 CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins' CompositorRunning: compiz Date: Thu Jan 10 21:02:07 2013 DistUpgraded: Fresh install DistroCodename: raring DistroVariant: ubuntu GraphicsCard: NVIDIA Corporation G80 [GeForce 8800 GTS] [10de:0193] (rev a2) (prog-if 00 [VGA controller]) Subsystem: Micro-Star International Co., Ltd. Device [1462:8010] InstallationDate: Installed on 2013-01-07 (3 days ago) InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Alpha amd64 (20130107) MachineType: System manufacturer System Product Name MarkForUpload: True ProcEnviron: TERM=xterm PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_US.UTF-8 SHELL=/bin/bash ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.7.0-7-generic root=UUID=55da2f7d-3310-4e8b-a53d-ad92b1fdb492 ro debug ignore_loglevel nomodeset SourcePackage: xserver-xorg-video-nouveau UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 03/09/2009 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: 2104 dmi.board.asset.tag: To Be Filled By O.E.M. dmi.board.name: P5B dmi.board.vendor: ASUSTeK Computer INC. dmi.board.version: Rev 1.xx dmi.chassis.asset.tag: Asset-1234567890 dmi.chassis.type: 3 dmi.chassis.vendor: Chassis Manufacture dmi.chassis.version: Chassis Version dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr2104:bd03/09/2009:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnP5B:rvrRev1.xx:cvnChassisManufacture:ct3:cvrChassisVersion: dmi.product.name: System Product Name dmi.product.version: System Version dmi.sys.vendor: System manufacturer version.compiz: compiz 1:0.9.9~daily12.12.05-0ubuntu2 version.ia32-libs: ia32-libs N/A version.libdrm2: libdrm2 2.4.40-1 version.libgl1-mesa-dri: libgl1-mesa-dri 9.0.1-0ubuntu1 version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A version.libgl1-mesa-glx: libgl1-mesa-glx 9.0.1-0ubuntu1 version.xserver-xorg-core: xserver-xorg-core 2:1.13.1.901-0ubuntu1 version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.7.3-0ubuntu2 version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.0.0-0ubuntu1 version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.20.17-0ubuntu1 version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.6-0ubuntu1 xserver.bootTime: Thu Jan 10 20:58:21 2013 xserver.configfile: default xserver.devices: input Power Button KEYBOARD, id 6 input Power Button KEYBOARD, id 7 input Microsoft Wired Keyboard 600 KEYBOARD, id 8 input Microsoft Wired Keyboard 600 KEYBOARD, id 9 input Logitech USB-PS/2 Optical Mouse MOUSE, id 10 xserver.logfile: /var/log/Xorg.0.log xserver.outputs: xserver.version: 2:1.13.1.901-0ubuntu1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-nouveau/+bug/1098316/+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