Hi ed, are you talking about an extreme level of zoom like zooming in 10000 times or something like that? There is a certain point where you will be running into precision issues with the floating point mathematics that are used for calculations.

But it's hard to know if that's what you're running into just from your description, it would help if you could please post a 3DM model file with the particular curve in it that you are having an issue with, then I could examine it over here and let you know if it's just something normal or if there is really an issue with it.

- Michael