  A D-dimensional gravitational model with a Gauss-Bonnet term and the
cosmological term Lambda is considered. By assuming diagonal cosmological
metrics, we find, for certain fine-tuned Lambda, a class of solutions with
exponential time dependence of two scale factors, governed by two Hubble-like
parameters H >0 and h < 0, corresponding to factor spaces of dimensions m > 3
and l > 1, respectively, with (m,l) non-equal to (6,6), (7,4), (9,3) and D = 1
+ m + l. Any of these solutions describes an exponential expansion of
3-dimensional subspace with Hubble parameter H and zero variation of the
effective gravitational constant G. We prove the stability of these solutions
in a class of cosmological solutions with diagonal metrics.
