I have *sometimes* this problem. I do '/etc/init.d/xdm stop' and the system thinks XDM is not running so it can't stop it (but it's there in tty7 and it works).
And sometimes, '/etc/init.d/xdm stop' works but when I go in tty7, I have something like "ÉÇÔZÈKËÄÅ" and I cannot go to the others tty. But I can have logging informations about dropped packets (like in bug #218631) and sys-request keys work and show infos. I don't know if the two problems are linked. My two cents. xdm 1:1.1.5-2 and 1:1.1.6-2