Overview:
Attempting to resize a window when using compiz+emerald causes the X server to crash.  The problem also occurs while hiding+showing a window when using kwin with compositing enabled.  If compositing is disabled the problem does not occur.

Steps to Reproduce:
1) Start X, compiz, and emerald, and create an xterm
2) Left-click a corner of the xterm window, and drag to resize
3) Release the button

Actual Results:
The X server crashes

Expected Results:
The X server doesn't crash, and the window is resized

Build Date & Platform:
26 July 2011 on Linux 3.0.0 x86_64 Gentoo

Additional Builds and Platforms:
Xorg server 1.10.2 also exhibits this problem.
Xorg server 1.9.5 works as expected.

Additional Information:
Sometimes it takes a few resize actions to cause the crash, and sometimes it happens with the first try.

I'm using the radeon driver with KMS disabled.  The Xorg.0.log file contains the following backtrace:

Backtrace:
[ 71067.040] 0: /usr/bin/X (xorg_backtrace+0x28) [0x45f528]
[ 71067.040] 1: /usr/bin/X (0x400000+0x63f29) [0x463f29]
[ 71067.040] 2: /lib64/libpthread.so.0 (0x7fbbaccf9000+0xf430) [0x7fbbacd08430]
[ 71067.040] 3: /usr/lib64/xorg/modules/extensions/libglx.so (0x7fbbaa8e6000+0x38d11) [0x7fbbaa91ed11]
[ 71067.040] 4: /usr/lib64/xorg/modules/extensions/libglx.so (0x7fbbaa8e6000+0x40aba) [0x7fbbaa926aba]
[ 71067.040] 5: /usr/lib64/xorg/modules/extensions/libglx.so (0x7fbbaa8e6000+0x37943) [0x7fbbaa91d943]
[ 71067.040] 6: /usr/bin/X (FreeResource+0x143) [0x44e2c3]
[ 71067.040] 7: /usr/lib64/xorg/modules/extensions/libglx.so (0x7fbbaa8e6000+0x34819) [0x7fbbaa91a819]
[ 71067.040] 8: /usr/lib64/xorg/modules/extensions/libglx.so (0x7fbbaa8e6000+0x37bd2) [0x7fbbaa91dbd2]
[ 71067.040] 9: /usr/bin/X (0x400000+0x30bb9) [0x430bb9]
[ 71067.040] 10: /usr/bin/X (0x400000+0x248da) [0x4248da]
[ 71067.040] 11: /lib64/libc.so.6 (__libc_start_main+0xfd) [0x7fbbabc6dd2d]
[ 71067.040] 12: /usr/bin/X (0x400000+0x24479) [0x424479]
[ 71067.040] Segmentation fault at address 0x240
[ 71067.040] 
Fatal server error:
[ 71067.040] Caught signal 11 (Segmentation fault). Server aborting