in a previous post i send a trouble on the unroll surface: http://python.rhino3d.com/threads/1009-UnrollSurface-bug?p=3992.
This was a bug in core Rhino and it was fixed.
Now I have the same trouble in the attached surface (it worked well some time ago): the id of the unrolled suface is [00000000-0000-0000-0000-000000000000] and the curve is correctly unfolded.
This is the code:
import rhinoscriptsyntax as rs
sup=rs.GetObject("select a surface",rs.filter.surface)
cur=rs.GetObjects("select curves", rs.filter.curve)