Makes sense and it works in the Properties panel when I save it over the default. If I use the Object Style Manager to set the stroke to fuscia and then to zero (like I did on the Properties panel) it does not work. In fact, if I change the color in Object Style Manager, set the stroke weight to zero, all the styles on the slides (and master slides) change to no hairline. Properties panel with save overwrite works like you suggest; Object Style Manager does not.
Cp7 (7.0.0.118), Win7-64
Thanks for your help. I have a work-around but it is not what I would call a solution, Can't imagine what the difference is between the overwrite of the Properties panel and setting the default in the Object Style Manager.