graphical problems

After upgrading from lenny/kde3 to squeeze/trinity, I have some graphical problems (mainly with kdm-trinity): -directly after boot the backgroud is some crapy picture from the last session -when I do a logout only I sometimes have a black screen (which is solvable by restarting the kdm-trinity from a remote host (switching to local consols on tha machin won't work (alt+ctrl+FX) useing a freshly installed/updated squeeze installation and the official trinity repos for that