  We consider the relationship between the temperature at which averaged energy
landscape properties change sharply ($T_{o}$), and the breakdown of mean-field
treatments of the dynamics of supercooled liquids. First, we show that the
solution of the wavevector dependent mode-coupling equations undergoes an
ergodic-nonergodic transition consistently close to $T_{o}$. Generalizing the
landscape concept to include hard-sphere systems, we show that the property of
inherent structures that changes near $T_{o}$ is governed more fundamentally by
packing and free volume than potential energy. Lastly, we study the finite-size
Random Orthogonal Model (ROM), and show that the onset of noticeable
corrections to mean-field behavior occurs at $T_{o}$. These results highlight
new connections between the energy landscape and mode-coupling approach to
supercooled liquids, and identify what features of the relaxation of
supercooled liquids are properly captured by mode-coupling theory.
