I think it can also be changed breaklines, point files and or boundaries.
Anything that defines the surface.
John
"Christinefsc" wrote in message
news:3447903.1112050320397.JavaMail.jive@jiveforum1.autodesk.com...
> Hi Todd,
>
> I believe that it means that you've made changes to the points used in
> your surface. If you made changes to your point group, like adding or
> deleting a point.
>
> Updating your point group and re-building your surface should fix this
> problem.
>
> This is all I know from past experiences. Hope it helps!
>
> Christine