It's a "bad" input file situation, but the simulator just sits there displaying "Loading chip..." in the bottom status line, rather than saying anything useful. One of my students this term managed to come up with this on the very first homework assignment.
I think the key point is that he tried to reference the chip being defined in the file defining it.
Here's one file that produces the problem:
(That's wrong in a couple of other ways as well, of course. I've redirected the student down what should be a more productive path for them, but it would be better if the HDL simulator didn't just sit there when given this sort of input.)