What could be the cause of the following error?

Hi everyone,

I am currently working on a optics project which requires me to automate using Visual Basic Application excel to run the lighting simulation. I have managed to run a Direct Simulation based on the no.of rays 20 M. The duration was about 15 min for 20 M.  However, once i run the direct simulation with more rays about 80 M the duration will be around 58 mins and the error will appear halfway through the simulation. I believe it has something to do with the session being disconnected.

Error :

Run-time error '-2147352567(80020009)':

pfcExceptions::XToolkitCommError

Thanks.

Best Regards,

Jerry