Curve fitting app crashing when increasing number of iterations

I'm trying to model a data set using a*sin(x)+b+c*erf(d*x+e), where a,b,c,d and e are coefficients that I would like the app to find. When I use the default number of iterations, I get a terrible fit for the data, which would clearly be well-fit by a function of the form above. When I increase the number of iterations, an error window from MATLAB pops up and forces the program to close. What is going on here? Is my computer simply not up to the task?