Comment 7 for bug 182288

Hey! A temporary solution that lets you use desktop effects!
I found it at http://ubuntuforums.org/showthread.php?t=676148
In the "All effects" tab enable "Present Windows" in the "Appearance" section. Click onto Settings and at the top select an option to activate the effect when the cursor is moved to a certain location on the screen. Apply everything. Now you can log out and try to log in again. You'll get the black screen... but... if you move the mouse cursor to where you set it to activate the effect, the effect will start up and everything will be back to normal.
This of course is only temporary, there's still a bug somewhere, but for those who want the effects this should work for the time being.
Richard