set from 1-300 and it only rendered one..? particle effects?? what kind, hardware or S/W (if it is S/W it will be next to the particle selection type in the AE).

mine used to render 10 or 100 or 36 .., whatever it felt like because the motherboard and processor was on the way out.., I got a new motherboard and had no problem since. so look out for that. At a guess, if you are using maya's software renderer, and using particles that need the hardware renderer that would be the problem, if you are using the hardware renderer maybe it just wont do it because your video card isnt up to it, maybe the specs are wrong or its old and open GL on your card is too old.

either ways, you may have a problem meaning $$$ unless it is something simple you have missed.

whatever, if its hardware you will have to do them (the particles) on a separate render pass and add them in a composite program like after effects.., maya will not render them in its software renderer.