xorg not remembering display settings in kde

[andrew]

I have this machine running with two users, myself with the kde 
desktop and principally using Kontact and Firefox, with my wife 
using gnome -evolution and firefox.

The ubuntu gnome session starts and runs fine but the kubuntu session 
defaults to 800 by 600 with 60Hz refresh. I can easily fix the size 
with Display-System settings but there are ephemeral effects which 
show xorg coonfiguration isn't using the same settings in kubuntu 
(kde) as ubuntu(gnome) nor is it remembering them between settings 
(presumably because they are faulty).

So how can I get the xorg configuration setting used by gnome into 
kde?

Andrew Heggie