  Let $M_c=M(2,0,c)$ be the moduli space of O(1)-semistable rank 2 torsion-free
sheaves with Chern classes $c_1=0$ and $c_2=c$ on a K3 surface $X$ where O(1)
is a generic ample line bundle on $X$. When $c=2n\geq4$ is even, $M_c$ is a
singular projective variety equipped with a symplectic structure on the smooth
locus. In this paper, we show that there is no crepant resolution of $M_{2n}$
for $n\geq 3$. This implies that there is no symplectic desingularization.
