  We reconcile seemingly conflicting statements in the literature about the
behavior of cosmological solutions in modified theories of gravity where the
Einstein-Hilbert Lagrangian for gravity is modified by the addition of a
function of the Ricci scalar, f(R). Using the example of f(R) = +/-\mu^4/R we
show that only such choices of f(R) where d^2f/dR^2>0 have stable
high-curvature limits and well-behaved cosmological solutions with a proper era
of matter domination. The remaining models enter a phase dominated by both
matter and scalar kinetic energy where the scalar curvature remains low.
