I only know some workarounds - but I believe there is a setting (that will hopefully be posted later on
When I urgently need X as root I do it over the KMenu -> system programs and somewhere there is the Filemanager in superuser mode. There you can log in as root and start the binaries manually.
Another method is to share you X Server with the root user. You have to enter the command xhost 127.0.0.1 as a normal user to allow "external" connections to the running XServer and then su and export DISPLAY=127.0.0.1:0 which will give your session a DISPLAY that X apps can use. Then you should be fine running X apps as root.
Another - and more sophisticated - way is to have two X login screens running. I haven't had the time to find out how yet but it is possible to have several Xs running just like you have several terminals running in runlevel 3.
So you can swith over (possibly with CTRL-ALT-F8) to the other XSession and login as root and run your program there. But... tell me how you did it if you figure it out.
Please consider that the first two solutions are merely a workaround but version 2 also works on a network if you replace the IPs respectively.