Artefacts in contour plot?

Results seem inconsistent; if i replace the

    > 'rosenbrock' function in my previous script with

The bug resulted from improperly initializing an array used in the
contour extension code. Fortunately Nadia has found and fixed it.
The changes are in CVS (colormaps and colorbars for contour too!) and
will be out in the next release, coming soon to theaters