I know this is not a rare problem. I've read the threads here regarding this for the most part and the advice I have picked up hasn't helped. I often get this message when trying to run apps in KDE as root:

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

I have tried xhost + and xhost + localhost and it doesn't seem to do anything. Of course, if I log in as root rather than just su to root I don't have this problem. So it is obviously a permissions issue. Does anybody know how to fix this? I haven't had this problem until I had to reinstall recently. Suggestions most appreciated.

BTW I run Debian. Thank you again.