We'd need a lot more info - Corona version, C4D version etc.
Also I am not clear what you are describing here. Did you run IR, everything looked good, you stopped it, you set 20 passes for your final render, and you began your final render? What resolution? Do you have a low memory warning? How much memory is Corona using, and how much does the system have installed? What does the image look like so we get an idea of the complexity of the scene (can screen grab it if you can't save it from IR due to everything being stuck). How long was it parsing for, 2 minutes, 5, 20?
Thanks!