  Ghost condensation has been recently proposed as a mechanism inducing the
spontaneous breaking of Lorentz symmetry. Corrections to the Newton potential
generated by a static source have been computed: they yield a limit M < 10 MeV
on the symmetry breaking scale, and - if the limit is saturated - they are
maximal at a distance L ~ 1000 km from the source. However, these corrections
propagate at a tiny velocity, v_s ~ 10^{-12} m/s, many orders of magnitude
smaller than the velocity of any plausible source. We compute the gravitational
potential taking the motion of the source into account: the standard Newton law
is recovered in this case, with negligible corrections for any distance from
the source up to astrophysical scales. Still, the vacuum of the theory is
unstable, and requiring stability over the lifetime of the Universe gives a
limit for M which is not too far from the one given above. In the absence of a
direct coupling of the ghost to matter, signatures of this model will have to
be searched in the form of exotic astrophysical events.
