Кажется, проблема была решена для меня, удалив Utopic HWE-Stack и понизив X.org и Kernel до исходной версии Trusty: Как удалить Kernel / LTS Enablement Stack?
uname -r возвращает:
3.13.0-48-generic
и Xorg -version:
X.Org X Server 1.15.1
Release Date: 2014-04-13
X Protocol Version 11, Revision 0
Build Operating System: Linux 3.2.0-76-generic x86_64 Ubuntu
Current Operating System: Linux nibbler 3.13.0-48-generic #80-Ubuntu SMP Thu Mar 12 11:16:15 UTC 2015 x86_64
Kernel command line: BOOT_IMAGE=/vmlinuz-3.13.0-48-generic root=/dev/mapper/lvmgroup01-ubuntu ro splash quiet vt.handoff=7
Build Date: 12 February 2015 02:49:29PM
xorg-server 2:1.15.1-0ubuntu2.7 (For technical support please see http://www.ubuntu.com/support)
Current version of pixman: 0.30.2
Before reporting problems, check http://wiki.x.org
to make sure that you have the latest version.