Hi Rich,
In playing around with this, I couldn't emulate the behavior you describe. What might help is the properties of the calling form (similar to what you posted for the preview form). I did note that with the preview form, setting the title bar off doesn't make any different. It'll have one regardless.
Anyway, post the properties of the calling form, and we'll get to the bottom of this.
George
Ubi caritas et amor, deus ibi est