  Quark matter at asymptotically high baryon chemical potential is in a color
superconducting state characterized by a gap Delta. We demonstrate that
although present weak-coupling calculations of Delta are formally correct for
mu -> Infinity, the contributions which have to this point been neglected are
large enough that present results can only be trusted for mu >> mu_c ~ 10^8
MeV. We make this argument by using the gauge dependence of the present
calculation as a diagnostic tool. It is known that the present calculation
yields a gauge invariant result for mu -> Infinity; we show, however, that the
gauge dependence of this result only begins to decrease for mu > mu_c, and
conclude that the result can certainly not be trusted for mu < mu_c. In an
appendix, we set up the calculation of the influence of the Meissner effect on
the magnitude of the gap. This contribution to Delta is, however, much smaller
than the neglected contributions whose absence we detect via the resulting
gauge dependence.
