(1) Open Terrain Builder 1.31.0.6950.
(2) Create a new project, and a mapframe in the project.
(3) Draw a simple polygon from "Shapes->Add Polygon".
(4) Open the "File->Export->Shapes..." dialog and with any "Source" and "Crop..." setting, save the shapefile somewhere.
(5) Clear the shapes layer in the "Shapes Tab" of the "Layers Manager" floating window, by right click the "default area".
(6) Open the "File->Import->Shapes..." dialog and select the shapefile that was saved in step 4.
(7) Note that the WKT is correct for the project settings (it should be, since it was generated by the project ;).
(8) Click "Ok". I expected at this point that it would import the shapefile, but instead it shows an error message.
Also:
* The exported shapefile is valid; it opens in numerous GIS packages without error.
* The issue also occurs if you delete the ".prj" file and use the coordinate system that Terrain Builder suggests.