We study tagged particle diffusion at large packing fractions, for a model of particles interacting with a generalized Lennard-Jones 2n-n potential, with large n. The resulting short range potential mimics interactions in colloidal systems. In agreement with previous calculations for short range potentials, we observe a diffusivity maximum as a function of temperature at constant density. By studying the temperature dependence of the configurational entropy which we evaluate with two different methods - we show that a configurational entropy maximum is observed at a temperature close to that of the diffusivity maximum. Our findings suggest a relation between the dynamics and number of distinct states for short range potentials. © 2005 IOP Publishing Ltd.