gnome-screensaver-preferences does not load

[Frank Jahnke]

The program "gnome-screensaver-preferences" does not load for me.  The
error message is:

pinot% gnome-screensaver-preferences --sync
** (gnome-screensaver-preferences:16652): DEBUG: Found best visual for
GL: 0x24
The program 'gnome-screensaver-preferences' received an X Window System
error.
This probably reflects a bug in the program.
The error was 'BadMatch (invalid parameter attributes)'.
(Details: serial 335 error_code 8 request_code 78 minor_code 0)

I was trying to correct a faulty screensaver: It blanks the left screen,
but not the right one, and there is nothing that can revive the left
screen.  FreeBSD 6.2-R-p7, xorg 7.3_1, Xinerama/nVidia 1.0.9639, Gnome
2.20.0 built yesterday.

Any advice?

Frank