remote x forwarding through ssh

[WarrenHead]

Hi list,

I'm trying to use ssh to forward X from a local FreeBSD server to my 
ubuntu machine.
I'm unable to get X forwarded. (ssh is working)

I set these options:
ubuntu:
/etc/ssh/ssh_config
Host *
ForwardX11 yes
ForwardAgent yes

FreeBSD
/etc/ssh/sshd_config
X11Forwarding yes
X11DisplayOffset 10
X11UseLocalhost yes
UseLogin no

I didn't set the $DISPLAY variable, on purpose.

After I log into the server and start xterm (for instance) I get this
message: DISPLAY is not set.
SSH should do that for me but I guess it doesn't.
I don't know why.

I logged into FreeBSD with these commands:
ssh -v freebsd
ssh -v -X freebsd
ssh -v -X -A freebsd

What could be the cause? Client or server?

Cheers, Warren