After selecting the imported object, you can open the group edit tool in Poser, create a new group, select the polygons that appear to have their normals flipped, and invert the group normals. But if they were backfaces to begin with, it means the other side won't show in preview mode. Poser will render backfaces according to the texture of the other side, but it can be disorienting. This happens with a model in areas that have no thickness (1-sided planes or surfaces). I don't recall if Ray Dream has an "Add thickness" command, but that's how I'd fix such a problem in Carrara. That way, there are no more backfaces to cause problems in Poser.