Comment 26 for bug 89189

That sounds like an issue with i810. I know that I have had that problem (with various other things, not directly with Desktop Effects) on an i810 setup with my Toshiba laptop. For example, sometimes switching from dual-head to single-head and back would make it so that a reboot was required before the X server would start back up again. X.org 7.2 seemed to fix most of those problems, though. Just a comment on the situation.