[Hampshire] X forwarding over ssh not working

Hello,

Client running Ubuntu 8.10 (yeah, yeah)
Server running Ubuntu 10.04

Server has "ForwardX11 yes" in /etc/ssh/ssh_config .

Client says ssh -X server
gets a conection to the server but if I then say 'xclock' I see nothing.
(I also see nothing on the desktop of the server).

If I connect with 'ssh -v' I see some trace info at the client:

victor@qg-backup:~$ xclock
debug1: client_input_channel_open: ctype x11 rchan 3 win 65536 max 16384
debug1: client_request_x11: request from 127.0.0.1 48169
debug1: channel 1: new [x11]
debug1: confirm x11

and then nothing.
When I Ctrl-C:

debug1: channel 1: FORCE input drain
^C
victor@qg-backup:~$ debug1: channel 1: free: x11, nchannels 2

I've never had trouble forwarding X over ssh before. Anything changed recently?

thanks,
victor