I don't know what happened to my post yesterday, BUT the Neutral (Yellow Wire) should NEVER EVER go to ground except at the service equipment. If the ballast is attached to the metal chassis, then there is no need to ground it. It should be connected to ground going back to the service panel. You having the yellow wires grounded is more than likely your problem as these guys stated.
By grounding the yellow wire, you are feeding the transformers inside the ballasts power, but they are not getting a return current which is possibly frying them (transformer) cause the current is flowing to the path of least resistance (which would be the chassis or case). Also, there is a huge risk for electric shock by touching the metal of the refrigerator cabinet, as you are providing a new route for current to flow. As I assume you know, transformers use a iron core wrapped in wire to step down or step up voltage. The load is never physically attached to the line on the transformer, but uses a magnetic field to carry the power across it.