  The energy in the ghost-free massive gravity theory is calculated via
explicitly resolving the initial value constraints for spherically symmetric
deformations of flat space. It turns out that the energy is positive in some
cases, but in other cases it can be negative and even unbounded from below.
This could suggest that ghost instability is present. However, it seems that
the negative energy states cannot communicate with the positive energy sector
since the corresponding solutions of the constraint equations are either not
globally defined, not asymptotically flat, or singular. As a result, they
cannot describe initial data for the decay of flat space. At the same time, for
globally regular and asymptotically flat solutions of the constraints the
energy is always found to be positive. All of this suggests that there is a
physical sector of the theory where the energy is positive and the ghost is
suppressed, so that the theory is stable. The negative energies show up only in
disjoint sectors and thus should be harmless.
