ssh and X11Forwarding

[Svante Signell <svante.signell@telia.com>]

When ssh-ing to a computer in my small LAN as a normal user and using
X applications, such as emacs, everything works OK. Howver, with su to
root on the remote box X is refused: Connection lost to X server`host:11.0'

Is the solution to be found with the X server or ssh/sshd?

X11Forwarding is enabled and Rootlogin disabled in the remote sshd and
X11Forwarding enable on the local ssh.

X has been working before, so probably some config files have changed
recently (I'm running sid/unstable). Openssh versions are 2.9p2.