Alright, I fixed it. It was ridiculously simple. But I'll post this up in case anyone else is having troubles.
My particles were set to a Layer that had a Scale Rate to 0, as well as the Parallax scrolling to 0, 0. Moving it to a layer that had its scale rate to 100, and parallax to 100, 100, fixed the problem.
So, if ever something is not working, check its scale rate & parallax scroll variables.