diomede: This might be better answered by philemot in the the thread "Carrara bridge to VWD questions". He set it up to address any issues regarding the Carrara Bridge.

I don't use the Carrara version, but I experience this on a regular basis with the DS Bridge. However, I believe it might be environmental, and not the software, because this only happens on my Windows XP laptop, but never on my W7 PC box.

For me, it is related to button clicking. If I simply left-click on the VWD buttons (collision, cloth, etc.) it will start to process (as in your scenario), but fails to create the OBJ, and I receive same error message. The work-around I have found to work is to left-click and hold button for a solid second, and then release. This seems to allow the OBJ creation function to finish, and everything works fine from there.

This hasn't been a repeatable bug on other systems, so you might be the second to encounter this (as far as I know). Please, try the slow-click method, and see if the process finishes without error.

This, of course, is just conjecture, because although similar, there are differences between the two bridges, and only philemot can really give you a proper diagnosis of the issue based on your variables.