Comment 7 for bug 639913

This also happens to me, but not at startup and I don't have an NVidia card. It seems like it might happen when I come out of suspend, but not consistently. Instructions on what details could make this report more useful to developers welcome!

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 27898 error_code 8 request_code 3 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.)