  We propose that the low temperature discrepancy between simple d-wave models
of the microwave conductivity and existing experiments on single crystals of
YBCO can be resolved by including the scattering of quasiparticles from "holes"
of the order parameter at impurity sites. Within a framework proposed
previously, we find in particular excellent agreement with data of Hosseini et
al. on slightly overdoped YBCO samples over the entire temperature range down
to about 2-3K, and for a wide range of frequencies. Remaining discrepancies in
the "universal" regime at very low temperatures are discussed.
