IS THE LOWEST ORDER SUPERSYMMETRIC WKB APPROXIMATION EXACT FOR ALL SHAPE INVARIANT POTENTIALS

It has previously been proved that the lowest order supersymmetric WKB approximation reproduces the exact bound state spectrum of shape inva riant potentials. We show that this is not true for a new, recently di scovered class of shape invariant potentials and analyse the reasons u nderlying this breakdown of the usual proof.