Particles winking in and out of existence? (particular)

So I picked up a copy of Trapcode's Particular, and was following Andrew Kramer's excellent tutorial on creating a bloodstream, when I hit a snag.
Everything works fine, except that some particles just...disappear for a frame. Not the same frame every time, some disappear on the same frame, others on other frames.

Here's an example (it's obviously not done yet):
http://www.mediafire.com/?w1j69rj3ylg

See how just after the second name is developed, the cells kinda...disappear for a frame or two? (You might have to scrub through)

Any ideas on what this is or how to fix it?
Robert Storm