Occasionally (reoccurring but not reliably reproducible) gnome-settings-daemon crashes with the following message in .xsession-errors

The program 'gnome-settings-daemon' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadMatch (invalid parameter attributes)'.
  (Details: serial 5183 error_code 8 request_code 15 minor_code 0)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)

This is noticeable since the sound theme and theme visual changes and several buttons show missing icon stubs.