It sounds like the file includes crossing vectors that do not represent a valid
combination of inside / outside entities.
To give you a feel for the level of complexity and file size that VCW can handle.
The eps file for the Celtic Maze
and Solution is 5Mb and contain 4,500 vectors.
The 3D toolpaths for this design take around 15 seconds to calculate.
E-mail the image file to - firstname.lastname@example.org
and we'll take a closer look.