With older ATI graphics cards with 32MB or less of video RAM some corruption of direct rendered windows, for example OSD notifier windows, might appear. This may be worked around by disabling ‘RenderAccel' in the Xorg configuration.
To do this first exit to the console using the following command:
sudo service gdm stop
Then create an Xorg configuration file with the command below:
sudo Xorg -configure
Then add the ‘RenderAccel' option to /etc/X11/xorg.conf:
Option "RenderAccel" "off"
And restart X/GDM.
sudo service gdm start