I also had problem exporting as .obj file. I was able to get around it somehow when I selected all parts of the object (if it concists of several parts). Grouped it and did a right click, choosed 'Bake polygons' (or something like that). After that I was able to export it as .obj file.
I'm not sure if it is the way to do it... but worth a try. :o)
Be sure to save the original first since it becomes one object.

Tiny