To attach a file use the Advanced Editor and look in the lower right corner.
I'm guessing there is a reversal in curvature or small kink that causes the surface to self-intersect or otherwise degenerate. Look at the curvature analysis (http://help.ptc.com/creo_hc/creo30_pma_hc/usascii/index.html#page/pma/surfacing/About_Curvature_Plot...)
I would have gotten there first, but stopped to get a link to the curvature analysis - new software, more confusing interface. Nice mention on scrolling.
Thank you gentlemen. This has been very helpful. I have attached some JPEG's of my latest curve, which shows a negative portion. Does CREO warn you of the inability to offset in this case? (I'm using CREO 2)
Back again -- I sure need to solve this! Attached is an extruded curve with a back bend. Works fine, so the issue with my pointy curves has to be with the curve at the point. I will play with this. Is it possible to manually modify these 3-D curves?