I'm running Arch. This happens with r300g but not with r600. I'm not exactly sure what triggers the mess, but running winecfg does it every time. The screen becomes unusable, but I am able to switch to a virtual terminal and restart X.

The best I can describe what I see is diagonal misplaced tiling, like repeating stairs from top left to bottom right across my screen.

I git-bisected to the very last commit before 6.14.0:

============================================================================
commit ef9bfb262db7004bef3704e5d914687e50d3fca4
Author: Alex Deucher <alexdeucher@gmail.com>
Date:   Tue Feb 1 19:24:44 2011 -0500

    kms/pre-6xx: fix pageflipping with tiling
    
    Use UTS/DFS to tile/untile as appropriate for sw access on
    pre-6xx.
    
    Fixes:
    https://bugs.freedesktop.org/show_bug.cgi?id=33738
    
    Signed-off-by: Alex Deucher <alexdeucher@gmail.com
============================================================================

mesa 7.10.0 (git built on Feb 6, 2011)
xorg-server 1.9.4

The specific card is: 01:00.0 VGA compatible controller: ATI Technologies Inc RV516 [Radeon X1300/X1550 Series]

There's nothing in the Xorg.#.log file at the default verbosity when this happens.