Troubles with FillRect and ToggleFullScreen


I’m just starting with SDL and have some troubles with FillRect and
ToggleFullScreen that I don’t understand. I just want to fill the
whole screen in one color, which works fine without fullscreen mode.
But as soon as I toggle to fullscreen mode, it doesn’t work anymore.
However, displaying a bitmap image does work.

Here is the code fragment:

screen = SDL_SetVideoMode(640, 480, 8, SDL_SWSURFACE|SDL_ANYFORMAT) ;
SDL_WM_ToggleFullScreen(screen) ;
color = SDL_MapRGB(screen->format, 255, 0, 0) ;
SDL_FillRect(screen, NULL, color) ;
SDL_UpdateRect(screen, 0, 0, 0, 0) ;

None of the SDL functions returns an error.

Is it a problem of the graphics card (Nvidia GeForce2 MX/MX 400,
latest 3123 driver) or of the distribution (SuSE 8.1)?

I really would appreciate some help on this.

Thanks a lot,