Problems simulating all of my source particles

Hi,

I am running a simulation by reading the phase space data for keV x-ray photons from a collision file.
The SOURCE user routine is able to read all the particles in the collision file (this is printed in the output log) but, for some reason, the code won't execute the simulation with all the particles in the collision file once it has read them. There were no errors in my geometry and when I ran the simulation with minimal geometry (just a collimator), I got the same problem.

I attach an example set of the relevant files.

I hope you can help.

Thanks.

Luke