have you done a particle cache?
select the particles
solvers>>create particle disk cache
(if you want to change the particles you need to delete this and re-do it)
then try rendering. Remember you don't assign shaders etc for hardware rendering so make sure that your particles have some colour so you can see them. Have you tried different particle types? e.g. multi streak just to see them a bit clearer. Is motion blur turned on? do you have enough samples?
Technical Director - Framestore
Currently working on: Your Highness