The dynamics of star polymers is investigated via extensive molecular and Brownian dynamics simulations for a large range of functionality f and packing fraction $\eta$. The calculated isodiffusivity curves display both minima and maxima as a function of $\eta$ and minima as a function of f. Simulation results are compared with theoretical predictions based on different approximations for the structure factor. In particular, the ideal glass transition line predicted by mode-coupling theory is shown to exactly track the isodiffusivity curves, offering a theoretical understanding for the observation of disordered arrested states in star-polymer solutions.