I had the same experience.

It turned out thet my xorg.conf file had been renamed with a .back suffix. I copied it back and restarted, and all was good.

On August 11, 2015 9:14:05 AM CEST, ciro santoro <email address hidden> wrote:
>I installed last updates on my ubuntu 14.04 and, after reboot, it
>starts
>and remains with a black screen.. I listened the ubuntu welcome sound
>and
>nothing appens :(
>
>2015-08-08 20:51 GMT+02:00 Nathanaël Naeri
><email address hidden>:
>
>> Packages nvidia-331-* are now transitional packages for version 340
>> where this bug has been fixed, so I guess they can be marked as Fix
>> Released too. Thanks everyone involved esp. Alberto for your work.
>>
>> --
>> You received this bug notification because you are subscribed to a
>> duplicate bug report (1409930).
>> https://bugs.launchpad.net/bugs/1431753
>>
>> Title:
>>   Nvidia binary driver FTBS due to DKMS layer violation
>>
>> Status in nvidia-graphics-drivers-331 package in Ubuntu:
>>   Confirmed
>> Status in nvidia-graphics-drivers-331-updates package in Ubuntu:
>>   Confirmed
>> Status in nvidia-graphics-drivers-340 package in Ubuntu:
>>   Fix Released
>> Status in nvidia-graphics-drivers-340-updates package in Ubuntu:
>>   Fix Released
>> Status in nvidia-graphics-drivers-346 package in Ubuntu:
>>   Fix Released
>> Status in nvidia-graphics-drivers-346-updates package in Ubuntu:
>>   Fix Released
>> Status in nvidia-graphics-drivers-331 source package in Trusty:
>>   Triaged
>> Status in nvidia-graphics-drivers-331-updates source package in
>Trusty:
>>   Triaged
>> Status in nvidia-graphics-drivers-340 source package in Trusty:
>>   Fix Released
>> Status in nvidia-graphics-drivers-340-updates source package in
>Trusty:
>>   Fix Released
>> Status in nvidia-graphics-drivers-346 source package in Trusty:
>>   Fix Released
>> Status in nvidia-graphics-drivers-346-updates source package in
>Trusty:
>>   Fix Released
>>
>> Bug description:
>>   Filing this against the 340-updates version but possibly the same
>>   applies to older versions, too. The nvidia source package produces
>two
>>   individual dkms packages: nvidia-340-updates,
>nvidia-340-updates-uvm.
>>   The problem is that the DKMS build of the nvidia-uvm module runs
>>   compile steps inside the nvidia modules build directory. This is
>>   violating the DKMS assumption that each module can be build
>>   independently (there is no way of describing cross-modules
>>   dependencies and even more important, the autoinstall step after a
>new
>>   kernel is installed will run the modules build in parallel).
>>
>>   Since nvidia and nvidia-uvm are very dependent on each other the
>right
>>   course of action seems to be to combine both sources in one DKMS
>>   module that produces two kernel modules (this is supported by
>DKMS).
>>   For the transition this resulting dkms package needs to have a
>>   breaks/replaces for the nvidia-uvm package.
>>
>> To manage notifications about this bug go to:
>>
>>
>https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-331/+bug/1431753/+subscriptions
>>
>
>
>-- 
>Ciro Santoro
>
>-- 
>You received this bug notification because you are subscribed to a
>duplicate bug report (1410245).
>https://bugs.launchpad.net/bugs/1431753
>
>Title:
>  Nvidia binary driver FTBS due to DKMS layer violation
>
>Status in nvidia-graphics-drivers-331 package in Ubuntu:
>  Confirmed
>Status in nvidia-graphics-drivers-331-updates package in Ubuntu:
>  Confirmed
>Status in nvidia-graphics-drivers-340 package in Ubuntu:
>  Fix Released
>Status in nvidia-graphics-drivers-340-updates package in Ubuntu:
>  Fix Released
>Status in nvidia-graphics-drivers-346 package in Ubuntu:
>  Fix Released
>Status in nvidia-graphics-drivers-346-updates package in Ubuntu:
>  Fix Released
>Status in nvidia-graphics-drivers-331 source package in Trusty:
>  Triaged
>Status in nvidia-graphics-drivers-331-updates source package in Trusty:
>  Triaged
>Status in nvidia-graphics-drivers-340 source package in Trusty:
>  Fix Released
>Status in nvidia-graphics-drivers-340-updates source package in Trusty:
>  Fix Released
>Status in nvidia-graphics-drivers-346 source package in Trusty:
>  Fix Released
>Status in nvidia-graphics-drivers-346-updates source package in Trusty:
>  Fix Released
>
>Bug description:
>  Filing this against the 340-updates version but possibly the same
> applies to older versions, too. The nvidia source package produces two
>  individual dkms packages: nvidia-340-updates, nvidia-340-updates-uvm.
>  The problem is that the DKMS build of the nvidia-uvm module runs
>  compile steps inside the nvidia modules build directory. This is
>  violating the DKMS assumption that each module can be build
>  independently (there is no way of describing cross-modules
> dependencies and even more important, the autoinstall step after a new
>  kernel is installed will run the modules build in parallel).
>
> Since nvidia and nvidia-uvm are very dependent on each other the right
>  course of action seems to be to combine both sources in one DKMS
>  module that produces two kernel modules (this is supported by DKMS).
>  For the transition this resulting dkms package needs to have a
>  breaks/replaces for the nvidia-uvm package.
>
>To manage notifications about this bug go to:
>https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-331/+bug/1431753/+subscriptions

-- 
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