how to remove Inf or NaN error from the model

I have modelled a vehicle model using simulink. After simulation i am getting this error : Derivative input 1 of '....../Subsystem4/Integrator1' at time 0.03 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). How to overcome this kind of error???? please guide me....