Version: (using KDE 4.0.3) Installed from: Fedora RPMs Right-click on desktop and select Lock Screen. Screen flashes and goes black (very briefly shows the "locked screen" dialogue box). The box still has focus, so typing one's password recovers the session. Occasionally before the black screen appears it shows a desktop with a different icon arrangement and wallpaper from usual, but this goes black at once. Intel mobo with 965 video chipset, Samsung 920NW LCD widescreen, Fedora 9 Preview + updates. kdebase-workspace-4.0.3-17.fc9.x86_64.
The mysterious desktop that flashes before going dark belongs to Gnome. I don't use Gnome but did once try it (so it's configured in my account). My display manager is KDM.
You should probably do 'killall nautilus' to get rid of the always-running GNOME desktop window. *** This bug has been marked as a duplicate of 157878 ***
Nautilus is indeed running, though I don't know why given that I'm not using Gnome. However killing it makes no difference to the flashing wallpaper.