  We present a computer simulation study of a disordered two-dimensional system
of localized interacting electrons at thermal equilibrium. It is shown that the
configuration of occupied sites within the Coulomb gap persistently changes at
temperatures much less than the gap width. This is accompanied by large time
dependent fluctuations of the site energies. The observed thermal equilibration
at low temperatures suggests a possible glass transition only at T=0. We
interpret the strong fluctuations in the occupation numbers and site energies
in terms of the drift of the system between multiple energy minima. The results
also imply that interacting electrons may be effectively delocalized within the
Coulomb gap. Insulating properties, such as hopping conduction, appear as a
result of long equilibration times associated with glassy dynamics. This may
shine new light on the relation between the metal-insulator transition and
glassy behavior.
