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