RW16: error message when importing 3d solid from Autocad

[MTetford]

Hi,

I've generated 3d striplogs for a site and now want to include a 3d cylinder and 3d box to represent a tank and a building on the site. I understood from the Rockworks help menu that I could import DXFs of 3d solids. I drew a cylinder and a box, as solids, in AutoCAD 2011 and exported them as Release 12 DXF versions (thinking that would be as simple a file as possible). When I import to Rockworks, though, I get an error message: "an unexpected entity [insert] has been found line 0".

Is there something special I need to do to the solid before I can import to Rockworks? I've seen colored cylinders, representing tanks, in some of the Rockworks promo material and would like to do the same for my project. How was it done, please? Maybe I'm not using the right approach?

Thanks,

Mira