Created attachment 111427 [details]
video screenshot of the glitch

When I enable 120Hz refresh rate in the Radeon R9 290 card, with my Benq
XL2420T monitor, I get horizontal glitches in the image. That happens in KDE,
Unity, XFCE (all with or without compositing), and games. Without compositing,
the windows decorations in KDE show artifacts in 60 and 120Hz.

60Hz refresh rate works okay. Fglx proprietary driver works okay with 120Hz. I
also have a Radeon HD 6970 with the radeon OSS driver and it also works okay in
120Hz in my system. 

Currently I am using Kubuntu 14.10, kernel 3.19RC1 and Mesa git from this PPA:
https://launchpad.net/~paulo-miguel-dias/+archive/ubuntu/mesa

The card is a Sapphire Radeon R9 290 4GB Tri-X.

This bug is happening since I got this card, in September.

I cant get a direct screenshot nor taking photos (with a smartphone) of the
glitch happening, so I take a video of it with a phone and then take a
screenshot.