Pathline problems

I am looking for help regarding Feflow particle tracking (pathlines).  Before I go to far, I should mention that I am currently using Feflow 5.3 and haven't upgraded to 6 yet.

I am running particles forward in my model and everything seems to work perfect with one exception.  The exception is when a particle exits the model via a pumping well.  When this happens, I get the log message, " WARNING: Math: Argument domain error in function ceil!".  At this point Feflow generally locks up and I need to go go into Windows task manager to exit out of Feflow.  When I say 'generally' locks up, I mean that it will lock up maybe 19 out of 20 attempts.  But every once in a rare while the particle tracking runs to completion. 

Any suggestions?  Thanks for any help.

Sorry.

try moving starting position(s) of the particles a little bit. you could probably also fix via an ifm module but that would be a serious programming effort.  upgrading to v6 would be most sensible.

Can this be done now?

I did not test the fieldline (e.g. pathlines) computations in FEFLOW 5.3. But newer FEFLOW versions definitely support fieldline computations.