Even though my Macbook Pro has an excellent graphics card, I still got a warning when I turned on Desktop Effects (Compiz). They work but I had (I think) more than my share of what seemed to be Compiz related crashes. But when things crash, the best thing to do is to not get upset and try to track down why it’s doing that. Compiz crashed as I was editing an OpenOffice document and for me that was the clue I needed apparently.
The system log showed that Compiz blew up inside of a file named libdecoration.so which led me to this forum post reply. The link he provides is broken (it should point here, but you can access the repository in question directly at http://download.opensuse.org/repositories/X11:/XGL/openSUSE_11.1/.
Since installing the updated Compiz packages, I haven’t had a screen lock or Compiz crash once (knock on wood).