  Orthogonal polynomials of degree $n$ with respect to the weight function
$W_\mu(x) = (1-\|x\|^2)^\mu$ on the unit ball in $\RR^d$ are known to satisfy
the partial differential equation $$
  [ \Delta - \la x, \nabla \ra^2 -
  (2 \mu +d) \la x, \nabla \ra \right ] P = -n(n+2 \mu+d) P $$ for $\mu > -1$.
The singular case of $\mu = -1,-2, ...$ is studied in this paper. Explicit
polynomial solutions are constructed and the equation for $\nu = -2,-3,...$ is
shown to have complete polynomial solutions if the dimension $d$ is odd. The
orthogonality of the solution is also discussed.
