It has to be that envSphere you have plugged into the reflection color on it's body, it just doesn't seem to play nice with the fire and it's not happening with the object that the plate is resting on. I made a bright green plane for it to reflect and it worked fine as long as the envSphere doesn't get a chance to kick in. You can rework the chrome shader and encapsulate the scene in a textured sphere or dome as NextDesign mentioned.