We consider the dynamical stability of a static brane model that incorporates
a three-index antisymmetric tensor field and has recently been proposed as a
possible solution to the cosmological constant problem. Ultimately, we are able
to establish the existence of time-dependent, purely gravitational
perturbations. As a consequence, the static solution of interest is
``dangerously'' located at an unstable saddle point. This outcome is suggestive
of a hidden fine tuning in what is an otherwise self-tuning model.Comment: 16 Pages, Latex; Discussion added but conclusions unchange
