Bug 710826

Sorry, however more info is needed to understand what is happening on your X session.

First of all, KDE has its own screensaver, kscreensaver. Are you sure that you are actually using xscreensaver instead of kscreensaver or something else?

( To check above, please post the results of following commands:
  $ rpm -qa | grep screensaver | sort
  $ ps auwwx | grep screensaver
)

[root@kali ~]# rpm -qa | grep screensaver | sort
gnome-screensaver-3.0.0-1.fc15.x86_64
kdeartwork-screensavers-4.6.3-1.fc15.x86_64
xscreensaver-5.14-1.fc15.x86_64
xscreensaver-base-5.14-1.fc15.x86_64
xscreensaver-extras-5.14-1.fc15.x86_64
xscreensaver-extras-base-5.14-1.fc15.x86_64
xscreensaver-extras-gss-5.14-1.fc15.x86_64
xscreensaver-gl-base-5.14-1.fc15.x86_64
xscreensaver-gl-extras-5.14-1.fc15.x86_64
xscreensaver-gl-extras-gss-5.14-1.fc15.x86_64
[root@kali ~]# ps auwwx | grep screensaver
root      2763  0.0  0.0 103428   856 pts/0    S+   15:12   0:00 grep --color=auto screensaver
[root@kali ~]# )

I only set the screen saver from within KDE. (Settings Control Panel)

I do not independently launch xscreensaver separately.

-gc

And how did you set screensaver on KDE "Control Panel"?

Also, from the output of ps no screensavers seem to be running. Would you relogin to KDE session and try "$ ps auwwx" again?

Well, kde has its own service for launching a screen saver.

You won't see it running, unless the service tracking the idletime says its time to launch it.

Secondly, I would like to point out, KDE desktop will use:

kscreenlocker to unlock the console on the root window for

keuphoria.kss, which is launched as the screen saver on the root window.

-gc

Okay, thank you. Changing the component to KDE ones

Sounds like X is crashing, i.e. a graphics driver bug. What graphics driver are you using?

name of display: :0
display: :0  screen: 0
direct rendering: Yes
server glx vendor string: SGI
server glx version string: 1.4
server glx extensions:
    GLX_ARB_multisample, GLX_EXT_import_context, GLX_EXT_texture_from_pixmap, 
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_MESA_copy_sub_buffer, 
    GLX_OML_swap_method, GLX_SGI_make_current_read, GLX_SGI_swap_control, 
    GLX_SGIS_multisample, GLX_SGIX_fbconfig, GLX_SGIX_pbuffer, 
    GLX_SGIX_visual_select_group, GLX_INTEL_swap_event
client glx vendor string: Mesa Project and SGI
client glx version string: 1.4
client glx extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, GLX_EXT_import_context, 
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_EXT_framebuffer_sRGB, 
    GLX_MESA_copy_sub_buffer, GLX_MESA_multithread_makecurrent, 
    GLX_MESA_swap_control, GLX_OML_swap_method, GLX_OML_sync_control, 
    GLX_SGI_make_current_read, GLX_SGI_swap_control, GLX_SGI_video_sync, 
    GLX_SGIS_multisample, GLX_SGIX_fbconfig, GLX_SGIX_pbuffer, 
    GLX_SGIX_visual_select_group, GLX_EXT_texture_from_pixmap, 
    GLX_INTEL_swap_event
GLX version: 1.4
GLX extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, GLX_EXT_import_context, 
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_MESA_copy_sub_buffer, 
    GLX_MESA_multithread_makecurrent, GLX_MESA_swap_control, 
    GLX_OML_swap_method, GLX_OML_sync_control, GLX_SGI_make_current_read, 
    GLX_SGI_swap_control, GLX_SGI_video_sync, GLX_SGIS_multisample, 
    GLX_SGIX_fbconfig, GLX_SGIX_pbuffer, GLX_SGIX_visual_select_group, 
    GLX_EXT_texture_from_pixmap, GLX_INTEL_swap_event
OpenGL vendor string: X.Org
OpenGL renderer string: Gallium 0.4 on AMD RV670
OpenGL version string: 2.1 Mesa 7.11-devel
OpenGL shading language version string: 1.20
OpenGL extensions:

The black screen when it does happen allows me to CTRL-ALT-BACKSPACE to kill the session.

So I think it might be a kwin compositor problem.

I checked the logs and did not find any output whatsoever of anything describing what happened.

So I don't think it is a kernel problem, or a X problem otherwise I wouldn't be able to continue using my machine.

-gc

Finished testing the latest ddx module for ATI video/X.

The last ati-ddx update I received has resolved this problem.

It also fixes full screen mode in Flash and  Stellararium.

-gc