I agree the scrambled background isn't an issue I
worry much about.
But this is: having logged of, I get the kdm loggin window. After a
while the monitor goes black for energy saving. From that point I only
get the screen back to life is to restart kdm-trinity remotely via ssh.
(moving mouse, pressing keys on the KB, switching the monitor off/on;
all that won't work).
Just out of curiosity: can you log in blind?