How to detect singularity in Simulink

Hi.

I want to ask a rather simple question, how do I solve this kind of error message?

"Error using prova2 (line 186) Derivative input 1 of 'PAC2002_Tire_Model/FL/Transient Behavior (Stretched String Model)/Integrator' at time 0.282000000000001 is Inf or NaN. Stopping simulation. There may be a singularity in the solution. If not, try reducing the step size (either by reducing the fixed step size or by tightening the error tolerances)"

This sort of error is happening almost anytime I build subsystem containing an integrator block. I have tried using a memory block upstream of my function block, have tried tracing out the states of the system by using the plot(tout, xout) command (link below), and yes, some of the states are detected by MATAB as NaN, but I don't know how to correct this problem. Can anyone please give me any other suggestions? I am just wasting time trying to figure out what could ever be wrong with the system. I just need to understand how to trace the source of the singuarity, and that should be enough to solve my problem.

(<http://it.mathworks.com/matlabcentral/answers/99084-why-am-i-receiving-error-messages-about-singularities-in-my-simulink-model>)

Thank you.