The fact that you have a suffixed object created means that the dress has been exported and reimported in Carrara. The message is from VWD. Objects have to be visible to be exported (same in Poser and Studio). After the first export, the original dress is hidden and the copy is visible. If you redo one without hidding or deleting the copy and making the original visible again, it won't work.

But all that doesn't account for the first export that should have worked. I had that kind of error when:

• the export takes too long. Most of the time, this is due to the "merge vertices" option checked with a high number of vertices.
• The obj file is locked. You may have to cleanup the exchange directory (there is an option in VWD Utilities menu).
• Carrara crashed somewhere in the process. that hasn't happened to me for a long time.

Hope that helps

Philemo