unable to open X window on machine

[David Cureton <david.cureton@catapult.com>]

Hi all,
	Firstly I must confess, I have not spent much time trying to sort this one 
out. However, I have the latest stable Debian installed in my machine running 
KDE desktop.  However I find that I am unable to cause other machines on the 
network to open an X window on my machine by setting the DISPLAY variable on 
the other remote machine before invoking xeyes, xclock or any other X 
application.
 
What I have done/tried:

1) Have run 'xhost + ' on X server to disable access control.

2) Can ssh to/from X server machine, network connectivity OK

3) Checked the iptables rules.  (Default policy on all is ACCEPT. no other 
rules except the defaults)

4) route output looks ok with only two entries. The local network entry and 
the default route entry which appear ok. (step 2 confirms this)

5) if DISPLAY is set to the machines own IP address 192.168.150.150:0.0, 
calling an X application fails due to 'Error: Can't open display: 
192.168.150.150:0.'. X applications only work when display is set to :0.0 on 
the local machine.

Is there some other type of access control I  am overlooking??

Cheers
David