The random-walk model of structural dynamics in supercooled liquids is generalized to account for long-range cooperative phenomena. Coupling of structural units within ordered clusters is shown to cause narrowing of the distribution function for the energies of structural units. As the temperature approaches a critical value T-K the ordered clusters expand, the distribution function approaches a delta-function, and the configurational entropy vanishes. This allows to identify the temperature T-K as the Kauzmann temperature. The model is also applied to the calculation of susceptibility spectra. The results are in quantitative agreement with existing experimental data.