The new entries layout in hosts which separate localhost and the
entry for the hostname results in ssh corrupting .Xauthority on
shared $HOME (for example home off NFS server).
The telltale symptom is not being able to launch any apps in KDE
after ssh-ing into another system which uses same $HOME directory.
IMO, in Lenny "X11UseLocalhost no" should be a _REQUIRED_ option
in /etc/ssh/sshd_config
The bug is posted a number of times versus KDE or other packages
in Ubuntu, but is in fact an ssh regression caused by the change
in /etc/hosts