when I upgrade from ubuntu 14.04 to ubuntu 15.10, after downloading the upgrades and installing, then the laptop goes blank, displays nothing, even when I reboot, it starts but it doesn't go to welcome screen, wents off again.

[Philemon Abel]

I want to upgrade from ubuntu 14.04 to ubuntu 15.10, but after updating the system software, and it tells me that my system is up to date, but there's a new version available, which is ubuntu 15.10, i agreed to upgrade, after upgrading, it downloads the upgrades, then it starts to install them, but before booting, the screen goes off, blank, nothing displays and I dont see any progress then, I waited for about morebthan seventy minutes but nothing happened, I decided to shut down the laptop manually, then I switched it on again, it starts to boot, displaying the name Ubuntu indicating that the system is loading, after few seconds before the welcome screen displays, it goes off again, displays nothing, that is, the screen become blank.

then I decided to reinstall ubuntu 14.04 from live dvd, .

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.8
ProcVersionSignature: Ubuntu 3.19.0-58.64~14.04.1-generic 3.19.8-ckt16
Uname: Linux 3.19.0-58-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Thu Apr 14 16:03:11 2016
InstallationDate: Installed on 2016-04-12 (1 days ago)
InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2016-04-14 (0 days ago)