Comment 27 for bug 588155

I doubt anyone will be able to fix this without a stack trace.

From what I can see, the current ddeb dbgsym packages have the gnome-settings-deamon binary in them which for some reason they didn't when I tried back with Lucid which made getting a stack trace impossible.

Since they now seem to work, Grab the dbgsym version and give the instructions I gave for logging gnome-settings-daemon a go. I would but it's no longer happening to me.

If the other instructions don't work or you want a different way, It might also be possible to rename dbgsym version of the /usr/bin/gnome-settings-daemon binary and replace it with script containing something like:
screen -L gdb --eval-command='run' gnome-settings-daemon.therealfile

Then just 'screen -x' and get a backtrace.