I dropped the patch from the recent karmic upload of gnome-power-manager. It is unclear whether this is still an issue in the new world where we just read -evdev events instead of ACPI events from hal, is pretty hackish, and it potentially leads to dropping valid events. I discussed it with Richard Hughes, and he suggested to try without the patch, and that he doesn't like to adopt it.
So I'd appreciate if folks could test version 2.27.2+git20090729 or above in karmic and check if they still get the problem. Thanks!