openSUSE 12.3
XFCE Desktop

Was working, then with a reboot the following no longer works attempting to "su to root" within a console, both XFCE Terminal and X-Term
Code:
su
su root
the error is
Code:
Incorrect Password
But, everything else which uses sudo and root permissions does work, eg
Code:
sudo /sbin/ifonfig
sudo yast
and
Launching YAST2 from menu

Also, logging into an XFCE session as root does still work

Years ago in an earlier openSUSE (11.1?) when I saw this in KDE, I was able to resolve with the following procedure which does not work
Login in Desktop Session as root
Reset password from within a console, using the same password
Code:
passwd
Logout and into a normal User session

Ideas?

TIA,
TSU