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?