This problem occurs oftenly. This is usually caused because of Inf or NaN output produced at a block. Set the diagnostic "Inf or NaN block output" to error in the configuration settings. If this is the issue, you will get the error as follows:
An error occurred while running the simulation and the simulation was terminated
- Block 'BlockName' outputs 'NaN' for element x of output port x at major time step 0
where BlockName is the block in which error is thrown.
You can debug your model from there to bypass NaN or Inf values from reaching the integrator.