  Lattice NRQCD has proven successful in describing the physics of the upsilon
system and B-mesons, though some concerns arise when it is used in simulations
of charm quarks. It is certainly possible that the NRQCD expansion is not
converging fast enough at this scale. We present some preliminary results on
the low-mass breakdown of NRQCD, in particular the behaviour of heavy
quarkonium and heavy-light meson spectra as the bare heavy quark mass is
decreased well below 1, with the aim of understanding more about the
manifestation of this breakdown.
