"Can't open display" after migrating from sarge to sid

[Dougie Nisbet <dougie@highmoor.co.uk>]

I upgraded to sid running KDE 3 last weekend. Now I find I can't display X 
apps from other hosts onto my PC. I've had a google around and tried a few 
things that I found in my searches but the problem persists.

I've tried:

--
Running 'xhost +' 
--
Using ssh -X
--
Using the x app on the command line. e.g.
	ssh -X nick /usr/bin/X11/xclock
--
Following the suggestions for file mods from 
http://lists.debian.org/debian-kde/2003/debian-kde-200301/msg00466.html - 
i.e.

/etc/ssh/sshd_config:

X11Forwarding no <- set this to yes

/etc/ssh/ssh_config

 #  ForwardAgent no  <-- Uncomment and set to yes
 #  ForwardX11 no     <-- Uncomment and set to yes
--
Editing /etc/X11/xinit/xserverrc and trying it with, and without the -nolisten 
tcp
--

And now I'm out of ideas. What else can I try?

Thanks,

Dougie