RE: Serious Problem!
I'm suffering from CRS right now and can't recall which bow it was, but it has happened to me. The cable should be taught at the moment, preventing the limbs from fully springing outward. Take it to the shop that installed the cable and get the new string (they are both usually replaced at the same time for this very reason) and you should be good to go.
Let the tech give it his blessing and I think you'll be fine.