SHM compositing lost with xorg-x11-server-Xorg 1.5.0-2

Hello,
  I did a routine upgrade on my up-to-date F9 x86_64 system with an ATI R500-
based card. After the upgrade, using shared memory for OpenGL compositing with 
kwin leads to screen corruption. I have reverted to using textures from 
pixmap, but I'd like to figure out why shared memory fails. Here are the 
relevant packages:
  mesa-libOSMesa-devel-7.1-1.fc9
  mesa-libGLU-devel-7.1-1.fc9   
  mesa-libGL-devel-7.1-1.fc9    
  mesa-libGLU-7.1-1.fc9         
  glx-utils-7.1-1.fc9           
  mesa-libGL-7.1-1.fc9          
  mesa-dri-drivers-7.1-1.fc9    
  mesa-libOSMesa-7.1-1.fc9      
  xorg-x11-server-Xorg-1.5.0-2.fc9
  xorg-x11-drv-ati-6.8.0-19.fc9
  kdebase-workspace-devel-4.1.1-1.fc9
  kdelibs-devel-4.1.1-12.fc9
Is there a known problem with SHM compositing on 1.5.0? Downgrading to a 
previous version of mesa does not fix it. The only extra option I have in my 
xorg.conf for this card is AccelMathod EXA. As far as I can tell, the only 
relevant packages updated are xorg-x11-server-* from a pre-1.5.0 version and 
kdelibs.

Should I prefer textures from pixmap (as opposed to shared memory) for 
compositing? My understanding is that SHM is faster but I am happy to stand 
corrected.

Regards,
Ravi




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