Does the Shuriken Particle System in Unity 4 not allow particles to render prior to collision?

I just upgraded to Unity 4, and so far I'm pretty happy with all the changes I've seen. I just encountered an issue with my particle systems though, and I was hoping someone might have an idea how to fix it.

I have a Shuriken particle system that spawns on the ground, rises until it hits a ceiling, and is set to collide with that ceiling, then float slowly down, as if a smoke cloud were hitting the ceiling and hanging at the top of the room. This worked perfectly in the previous version of Unity, but with Unity 4, the particles only seem to appear AFTER the collision, and not prior to that. If I turn on wireframes, I can see the particle wireframes spawn at origin, and then disappear completely until reaching the collision, at which point the wireframe and particles become visible again.

Has anyone else encountered this? Is there a setting in Unity 4 that I have to adjust that I'm unaware of?

Thanks for the help!