The symptoms suggest that gnome-settings-daemon is crashing. Perhaps you could run it with strace to see what causes it to exit, if it's not a crash.
Something like this:
# somehow kill the current gnome-settings-daemon instance
# then run a new one with strace:
strace gnome-settings-daemon 2>/tmp/gsd.strace &
# once you repro the symptoms, the end of the strace file should show what gsd did
# just before it quit
If you cannot interpret the file yourself, feel free to attach it here.
The symptoms suggest that gnome-settings- daemon is crashing. Perhaps you could run it with strace to see what causes it to exit, if it's not a crash.
Something like this:
# somehow kill the current gnome-settings- daemon instance daemon 2>/tmp/gsd.strace &
# then run a new one with strace:
strace gnome-settings-
# once you repro the symptoms, the end of the strace file should show what gsd did
# just before it quit
If you cannot interpret the file yourself, feel free to attach it here.