There can be many causes for this error.
One example is if there is no mass in your system. Simulink will try to solve "F=ma", but if there is no mass, the acceleration will be infinite.
Other models that are "too ideal" can cause such problem.
Usually, you work around such problem by making your model more realistic, by including damping or masses in your system.
Without the model, it is difficult to diagnose more accurately.