  We establish a relation between time-like, light-like and space-like orbits
of the non-compact E{7(7)}(R)symmetry and discrete E{7(7)}(Z) invariants. We
discuss the U-duality invariant formula for the degeneracy of states d(Q) which
in the approximation of large occupation numbers reproduces the
Bekenstein-Hawking entropy formula for regular black holes with AdS_2 horizon.
We explain why the states belonging to light-like orbits, corresponding to
classical solutions of "light black holes with null singularity", decouple from
the corresponding index. We also present a separate U-duality invariant formula
for the class of light-like orbits specified by discrete E{7(7)}(Z) invariants.
We conclude that the present study of the non-perturbative sector of the theory
does not reveal any contradiction with the conjectured all-loop perturbative
finiteness of D=4 N=8 supergravity.
