  We consider a periodic lattice rapidly driven through a quenched random
potential as a model of a moving Abrikosov lattice. In addition to the
transverse phonon displacements $u_y$, we consider the displacements $u_x$
along the direction of motion, which were assumed to be small in earlier
treatments. We show that these displacements are in fact divergent even on
large length scales and therefore lead to a breakdown of the elastic model
along the direction of motion. We propose that the resulting phase is a moving
"smectic" with translational order that is quasi-long-range transverse and
liquid-like parallel to the direction of motion.
