The normalized in-plane magnetoconductivity of the dilute strongly interacting system of electrons in silicon MOSFET's scales with $B/T$ for low densities in the insulating phase. Pronounced deviations occur at higher metallic-like densities, where a new energy scale $k_B ��$ emerges which is not associated with either magnetic field or thermal effects. $B/T$ scaling of the magnetoconductivity breaks down at the density $n_0$ where the energy scale $k_B ��$ vanishes, near or at the critical density $n_c$ for the apparent metal-insulator transition. The different behavior of the magnetoconductivity at low and high densities suggests the existence of two distinct phases.

4 pages, 5 figures