Last week I reinstalled Ubuntu 14.04 on my laptop and since then I'm experiencing strange short horizontal flicker. It's hard to describe so here is a video of it and this is my current setup:

lspci -nn | grep VGA

01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] RV710/M92 [Mobility Radeon HD 4330/4350/4550] [1002:9552]

glxinfo | grep "renderer string"

OpenGL renderer string: Gallium 0.4 on AMD RV710

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 zander-pc 3.16.0-34-generic #47~14.04.1-Ubuntu SMP Fri Apr 10 17:49:16 UTC 2015 x86_64

Kernel command line: BOOT_IMAGE=/boot/vmlinuz-3.16.0-34-generic root=UUID=dab06a14-8d7a-4d9d-a4da-24dee36894a9 ro quiet splash 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.

My first thought was to install the proprietary ati driver (flgrx, legacy) but that messed up my xserver so badly that I had to reinstall Ubuntu again. So then I wondered why the problem had not occured with my old installation of Ubuntu 14.04. The only difference is that I'm now running a 64bit version.

So I think I'm stuck with the open source drivers, i.e. xserver-xorg-video-radeon, but that wouldn't be such a bad thing if this flickering problem could somehow be fixed. I did a lot of research and tried a bunch of things such as defining other options of the driver in /etc/X11/xorg.conf or specifying options for the module in /root/defaults/grub an running grub-update but none of this changed anything. I can't think of anything more to do.