Here's what I did:
1. opened monitor settings and set monitor rotation to "counterclockwise" (+ confirm and pivot monitor)
2. restarted computer (while leaving monitor tilted)
3. logged in under same account (a bit awkward, since login screen is not rotated)
Result:
At first the black screen with the text based system log appears as usual, but it stays and is not replaced by the unity desktop. However, the mouse pointer is visible and I can actually activate functions from an invisible menu by guessing the menu item's position.
This effect only shows, when the monitor is rotated.
I found 2 possible workarounds:
1) First log in as a different user (with regular rotation settings), then log off and again log in under original account (with 90° rotation).
2) Always switch back the rotation setting when shutting down the computer.
ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: xorg 1:7.6+7ubuntu7.1
ProcVersionSignature: Ubuntu 3.0.0-16.29-generic 3.0.20
Uname: Linux 3.0.0-16-generic i686
.tmp.unity.support.test.0:
ApportVersion: 1.23-0ubuntu4
Architecture: i386
CompizPlugins: [core,bailer,detection,composite,opengl,decor,compiztoolbox,mousepoll,imgpng,resize,move,unitymtgrabhandles,regex,snap,animation,grid,gnomecompat,vpswitch,place,wall,session,workarounds,expo,fade,scale,ezoom,unityshell]
CompositorRunning: compiz
Date: Mon Mar 12 19:02:06 2012
DistUpgraded: Log time: 2011-10-22 13:57:30.730852
DistroCodename: oneiric
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes, if not too technical
GraphicsCard:
Intel Corporation N10 Family Integrated Graphics Controller [8086:a001] (rev 02) (prog-if 00 [VGA controller])
Subsystem: ASUSTeK Computer Inc. Device [1043:83e6]
Subsystem: ASUSTeK Computer Inc. Device [1043:83e6]
InstallationMedia: Ubuntu-Netbook 10.10 "Maverick Meerkat" - Release i386 (20101007)
MachineType: System manufacturer System Product Name
ProcEnviron:
PATH=(custom, no user)
LANG=de_DE.UTF-8
SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.0.0-16-generic root=UUID=b33cf3b4-9e5f-416c-9c72-c68556d5b913 ro quiet splash vt.handoff=7
SourcePackage: xorg
Symptom: display
UpgradeStatus: Upgraded to oneiric on 2011-10-22 (142 days ago)
dmi.bios.date: 03/15/2010
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 0405
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: AT5NM10-I
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: Rev x.0x
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr0405:bd03/15/2010:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnAT5NM10-I:rvrRevx.0x:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.name: System Product Name
dmi.product.version: System Version
dmi.sys.vendor: System manufacturer
version.compiz: compiz 1:0.9.6+bzr20110929-0ubuntu6.1
version.libdrm2: libdrm2 2.4.26-1ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 7.11-0ubuntu3
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 7.11-0ubuntu3
version.xserver-xorg: xserver-xorg 1:7.6+7ubuntu7.1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.6.0-1ubuntu13
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.14.99~git20110811.g93fc084-0ubuntu1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.15.901-1ubuntu2.1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:0.0.16+git20110411+8378443-1
It sounds very much like the randr bug fixed in Xorg, but I can't see the usual suspects in the attached files. Presuming fixed, please do retest on raring.