GZDoom 2.1.1 Visual Artifacts

[Nines]

I'm experiencing some weird graphical glitches. Basically, everything on the screen is flickering, including text and menus. Here is the screenshot: http://i.picpar.com/Z6Jb.jpg
This is vanilla, with default settings, without any mods, with Ultimate Doom .wad.

[Rachael]

1) When was your last display driver update?
2) Does it still happen on 1.9.1?

[Nines]

1) 2014. I would like to update it, but there won't be any new versions.
2) No.

[Graf Zahl]

What operating system?
What graphics hardware?

[Nines]

WinXP
AMD Radeon HD 6570 with 1GB of VRAM, running on Catalyst 14.4.

[Graf Zahl]

Since AMD has repeatedly released broken drivers, if there are no more upgrades, the only alternative thing to try would be downgrading the driver to an older revision.

[Nines]

I'll stick with 1.9.1 then. Zandronum 2/3 are also working fine, but there are some problems with one of the mods (it's not fully compatible it).

[Graf Zahl]

This should be fine now, except for the dynamic lights which are being worked on.