I will try to get something packaged up and sent over to you via PM if that is okay. I have people models and animation files that are not ready to full public sharing. I am using a rail clone placeholder object to scatter the people using forest, similar to the parking lot tutorial. Would that have anything to do with it?
It's also a stadium, so we're about 4,000 animated people in total. 6 people models with 8 different point cache files and random sample are set for the animation in forest. I don't get a warning that limits have been hit as the first frame renders just fine, but could it just be too much information?