Black screen after logging in, after installing Nvidia-CUDA

[NoBugs!]

After installing Nvidia-CUDA* packages, Unity breaks. There's only black screen after logging in, even when I remove the Nvidia-CUDA packages. please advise.

sudo dpkg-reconfigure xorg doesn't help at all either.

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: unity 7.1.2+13.10.20131014.1-0ubuntu1
ProcVersionSignature: Ubuntu 3.11.0-15.23-generic 3.11.10
Uname: Linux 3.11.0-15-generic x86_64
NonfreeKernelModules: nvidia
.proc.driver.nvidia.gpus.0: Error: [Errno 21] Is a directory: '/proc/driver/nvidia/gpus/0'
.proc.driver.nvidia.registry: Binary: ""
.proc.driver.nvidia.version:
 NVRM version: NVIDIA UNIX x86_64 Kernel Module 304.88 Wed Mar 27 14:26:46 PDT 2013
 GCC version: gcc version 4.8.1 (Ubuntu/Linaro 4.8.1-10ubuntu9)
ApportVersion: 2.12.5-0ubuntu2.2
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
Date: Sat Jan 11 13:58:28 2014
DistUpgraded: Fresh install
DistroCodename: saucy
DistroVariant: ubuntu
DkmsStatus: nvidia-304, 304.88, 3.11.0-15-generic, x86_64: installed
EcryptfsInUse: Yes
GraphicsCard:
 Intel Corporation 3rd Gen Core processor Graphics Controller [8086:0166] (rev 09) (prog-if 00 [VGA controller])
   Subsystem: Dell Device [1028:054e]
   Subsystem: Dell GeForce GT 630M [1028:054e]
InstallationDate: Installed on 2013-11-23 (49 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
MachineType: Dell Inc. XPS L521X
MarkForUpload: True
ProcEnviron:
 TERM=linux
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.11.0-15-generic.efi.signed root=UUID=8e997c12-0ee0-422b-a7e4-a7cb0a74f38f ro quiet splash vt.handoff=7
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/22/2013
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A14
dmi.board.name: 0C5Y96
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: A14
dmi.modalias: dmi:bvnDellInc.:bvrA14:bd05/22/2013:svnDellInc.:pnXPSL521X:pvrA14:rvnDellInc.:rn0C5Y96:rvrA00:cvnDellInc.:ct8:cvrA14:
dmi.product.name: XPS L521X
dmi.product.version: A14
dmi.sys.vendor: Dell Inc.
version.compiz: compiz 1:0.9.10+13.10.20131011-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.46-1ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 9.2.1-1ubuntu3
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 9.2.1-1ubuntu3
version.nvidia-graphics-drivers: nvidia-graphics-drivers N/A
version.xserver-xorg-core: xserver-xorg-core 2:1.14.5-1ubuntu2~saucy1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.7.3-0ubuntu3.1
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.2.0-0ubuntu10
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.904-0ubuntu2
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.9-2ubuntu1
xserver.bootTime: Sat Jan 11 13:50:26 2014
xserver.configfile: default
xserver.errors: Failed to initialize GLX extension (Compatible NVIDIA X driver not found)
xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:
 product id 4333
 vendor AUO
xserver.version: 2:1.14.5-1ubuntu2~saucy1

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Pablo (itu-pablo)]

I have this issue in 15.04 (Vivid). Installed Cuda-7.5 from Ubuntu repo and it breaks X (on top of nvidia-352). In my case, I can't even get to the login screen. Starting Ubuntu in recovery mode and selecting 'Resume Boot' does get me to the login screen, but login attempts throw me back to the same screen.

I managed to pinpoint the problem to the nvidia-modprobe package (require by CUDA), which breaks my graphics.