  We present the results of an experimental study of the current-voltage
characteristics in strong magnetic field ($B$) of disordered, superconducting,
thin-films of amorphous Indium-Oxide. As the $B$ strength is increased
superconductivity degrades, until a critical field ($B_c$) where the system is
forced into an insulating state. We show that the differential conductance
measured in the insulating phase vanishes abruptly below a well-defined
temperature, resulting in a clear threshold for conduction. Our results
indicate that a new collective state emerges in two-dimensional superconductors
at high $B$.
