https://bugs.freedesktop.org/show_bug.cgi?id=59015
--- Comment #9 from Adam Jorgensen adam.jorgensen.za@gmail.com --- (In reply to comment #5)
I'm assuming you are using mesa 9.x or newer based on the version info in the bug header. Can you confirm? xf86-video-ati 7.0.0 requires mesa 9.x. Also, if the steam client is a 32-bit application and you are running a 64-bit distro, you will need to make sure your 32-bit 3D driver is up to date. I suspect you have an out of date 32-bit 3D driver.
I can confirm that I am using Mesa 9.0.1 in conjunction with xf86-video-ati 7.0.0.
I *thought* I was running Steam as a 64-bit application but based on the lack of an "ubuntu12_64" directory in my ~/.local/share/Steam directory it seems likely that my Steam installation is actually a 32-bit one.
I am using the latest emul-x86 libs (I'm running Sabayon Linux) but I also have a separate 32-bit chroot for work purposes. I will try updating the chroot environment (Since it's set up with the same distro) and installing Steam their and testing it in that environment...