KDESU cannot find program 'su'

[nicoDVD2]

Whe I try to open a configuration application or something that requieres root, I get this error.

But "su" is installing and working, within terminal off course.
Any Idea ??

my box:

Knoppix 5.1 on HD.
root@linux:/dev# uname -a
Linux linux 2.6.19 #7 SMP PREEMPT Sun Dec 17 22:01:07 CET 2006 i686 GNU/Linux

[hal8000]

Thats an old error fixed posted some time ago. From memory,
The fix was to issue visudo from a terminal and add user knoppix,
post back if you still have trouble.