Can't play video and fall to emergency mode

If I play a video, it continues for a while then stop and the screen is black in Dragon Player. In most of time, I'll fall to emergency mode.
Note: I've a problem. I can only login through systemctl defaul command in the emergency mode.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: fglrx 2:15.200-0ubuntu4
ProcVersionSignature: Ubuntu 3.19.0-21.21-generic 3.19.8
Uname: Linux 3.19.0-21-generic x86_64
NonfreeKernelModules: fglrx
ApportVersion: 2.17.2-0ubuntu1.1
Architecture: amd64
CurrentDesktop: KDE
Date: Thu Jun 18 00:53:11 2015
InstallationDate: Installed on 2015-06-09 (8 days ago)
InstallationMedia: Kubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
ProcEnviron:
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: fglrx-installer
UpgradeStatus: No upgrade log present (probably fresh install)