I had this happen to me on a few occasions when I first started using Bryce Unfortunately it happened with a mesh that had a ton of individual objects and after hours of work. I rendered the scene and this robot I was working with looked all out of shape. When I examined it closer I noticed many elements slightly out of place or scaled unequally. I learned that if you manipulate a group of objects especially if they all part of the same figure, just by selecting the different elements the figure can become distorted. To avoid this after selecting all of the sub-elements group them by clicking on the little G button. This will prevent the distortion.