Problem with changing parameter estimates

Hello all, I am running nonmem 6, using wings for nonmem. I have ran into a slight problem. Whilst gradually building up a model, an initial value for a parameter was changed. This caused many executable files to be created in the control file folder, and the run to go on infinitely as if in an infinite loop. Anyone any ideas on what happened? The change in the initial parameter value was the only difference in this particular control file to the others, and it was the 14th run at that point. As always, much obliged to anyone with any replies. Best Regards, Paul Westwood.