Client is not authorised to connect to server

[Rachel Andrew <lists@rachelandrew.co.uk>]

Hi

after upgrading my woody box to kernel 2.4.16 I now cannot run any x 
applications from a terminal window, having su'd to root while logged in as 
my user. I get a message 'Cannot connect to X Server: 0.0'

I can connect if I start X with startx when logged in from the shell, but if 
X is started up by kdm I get this error. I'm having problems with a couple of 
KDE apps and am wondering if this is the cause of it and so would like to 
findout what might be going on here! I'm sure its a simple fix but I haven't 
found it yet!

Any suggestions would be greatly appreciated.

Rachel