For a while my keyboard wasn't functioning every time at bootup to KDM due to getty stealing the keyboard to vt2, so I had to drop to console and do /etc/init.d/kdm restart.
This seems to fix the problem:

mcedit /etc/kde3/kdm/Xservers
Add vt7 to the end of this line:
:0 local@tty1 /usr/X11R6/bin/X -nolisten tcp vt7

mcedit /etc/kde3/kdm/kdmrc
Add ServerVTs=-7 to the General section:
[General]
ConfigVersion=2.1
PidFile=/var/run/kdm.pid
Xservers=/etc/kde3/kdm/Xservers
ServerVTs=-7