As I had the same problems I tried to modify my xorg.conf. What helps was to disable DRI2 and enable DRI. My working xorg.conf for my radeon 7000 (M6LY):
Section "Device" Identifier "Configured Video Device" Option "AGPMode" "4" Option "AGPSize" "32" Option "DRI" "true" Option "DRI2" "false" EndSection
RenderAccel is XAA per default.
Working means that notifications and compiz work as expected.
As I had the same problems I tried to modify my xorg.conf. What helps was to disable DRI2 and enable DRI. My working xorg.conf for my radeon 7000 (M6LY):
Section "Device"
Identifier "Configured Video Device"
Option "AGPMode" "4"
Option "AGPSize" "32"
Option "DRI" "true"
Option "DRI2" "false"
EndSection
RenderAccel is XAA per default.
Working means that notifications and compiz work as expected.