Installing Compiz again as well as the other proposed packages, with intrepid-proposed checked, did not change the situation: enabling "Normal" desktop effects (System > Preferences > Appearance) still causes the X session to freeze (keyboard stops responding, windows and panels disappear, and the only way out is to hard-reboot) after "searching for available drivers" for a moment. So it is pretty much the same as in Jerry's case, except that the screen does not "go to hash" (if I understood this correctly — in my non-native speaker's vocabulary, hash is the "#" sign...), but all I can see is the wallpaper and mouse pointer (which I can still move). Sorry to say.
Installing Compiz again as well as the other proposed packages, with intrepid-proposed checked, did not change the situation: enabling "Normal" desktop effects (System > Preferences > Appearance) still causes the X session to freeze (keyboard stops responding, windows and panels disappear, and the only way out is to hard-reboot) after "searching for available drivers" for a moment. So it is pretty much the same as in Jerry's case, except that the screen does not "go to hash" (if I understood this correctly — in my non-native speaker's vocabulary, hash is the "#" sign...), but all I can see is the wallpaper and mouse pointer (which I can still move). Sorry to say.