Unlike my previously successful hard disk Knoppix installations (various versions from 3.1 to 3.4) my latest HD installation (3.8.1) does not result in root being one of the user options for selection once the boot process has finished. I can login as a normal user, and successfully su into root via a terminal window, but if I then try to start Konqueror from the command line I get the following:-

Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

konqueror: cannot connect to X server :0.0

How can I run root from a KDE graphical interface using Knoppix 3.8.1, as I am used to doing using Knoppix 3.3?
The rest of the installation works fine, and I am even able to print from a network printer which previously required editing of cups and kde configuration files.
Thanks for any advice.