help: FC19, FC20 desktop turned black

[Charlie Zender]

Hi,
After running my FC19 laptop without rebooting for many months,
I rebooted and of course things had changed (due to updates) so
the system failed to come up correctly. Specifically the login
screen was fine but the KDE background is now all black except
for the cursor which has a white outline. Since I can't see the
workspace, it is useless. From the terminal command line I then
upgraded to FC20 but unfortunately the same problem persists.
KDE Failsafe mode works fine, though (background is not black).
Gnome desktop complains of an error and refuses to start.
How do you recommend I restore the KDE background?
Thanks!
cz
p.s. Hardware is Dell Precision M6400 laptop with NVidia Quadro
FX 3700M video card.
-- 
Charlie Zender, Earth System Sci. & Computer Sci.
University of California, Irvine 949-891-2429 )'(