  The presence of a viscous boundary layer under the solid crust of a neutron
star dramatically increases the viscous damping rate of the fluid r-modes. We
improve previous estimates of this damping rate by including the effect of the
Coriolis force on the boundary-layer eigenfunction and by using more realistic
neutron-star models. If the crust is assumed to be perfectly rigid, the
gravitational radiation driven instability in the r-modes is completely
suppressed in neutron stars colder than about 1.5 x 10^8 K. Energy generation
in the boundary layer will heat the star, and will even melt the crust if the
amplitude of the r-mode is large enough. We solve the heat equation explicitly
(including the effects of thermal conduction and neutrino emission) and find
that the r-mode amplitude needed to melt the crust is approximately a_c = 5 x
10^{-3} for maximally rotating neutron stars. If the r-mode saturates at an
amplitude larger than a_c, the heat generated is sufficient to maintain the
outer layers of the star in a mixed fluid-solid state analogous to the pack ice
on the fringes of the Arctic Ocean. We argue that in young, rapidly rotating
neutron stars this effect considerably delays the formation of the crust. By
considering the dissipation in the ice flow, we show that the final spin
frequency of stars with r-mode amplitude of order unity is close to the value
estimated for fluid stars without a crust.
