Simulink model only runs once

I can run a Simulink model once in 2007b.

If I press stop and run again the model crashes stating the level 2 s-functions do not exist.

The m files don't get deleted during the simulation and the current directory doesn't change.

The only way to be able to run a new experiment is to close MATLAB completely and re-open it.

Any ideas?

[Abhishek M]

is your model acquiring inputs through an external file or in the same model??