Time list must not be zero

Hi

I'm currently modelling a magnetic bottle for photoelectronspectroscopy. As a part of the model I'm interested in the particle trajectories. When I try to run the time dependent study in the charged particle mode, I always get the error "Time list must not be zero". Can you help me to find the error?

I'm using COMSOL 4.2a

Yours sincerly
Jorge Ferreiro