Where does the calculation freeze? If I have a complex model involving lots of porous media the solver may be stuck on "Collecting volumetric porous..." for a long time (almost an hour once) but it does eventually solve the model.
GDI is unlikely the issue
you have to mesh the porous medium so it sounds like you're hitting the limit of your resources. how much ram do you have? how much are you using? how many cells are created in both cases? what operating system are you using?