Particle emitter stops and starts, seemingly randomly

I have a particle emitter which is raining down particles (Line shape, 0˚ emission range) All goes well, until I get to frame 900 (and 1800, and 2700 etc...). At this point the particles stop, semmingly automatically, until 102 frames later when the stream of particles starts up again. This continues throughout the composition, every 900 frames or so. I am wondering if there is a solution to this, or a workaround.

Thanks