Creating vertex objects from spline objects does creates a lot of unwanted artifacts. To clean up a vertex model I found that selecting small segments of the vertex object and welding it using a small tolerance will work. I've tried selecting the whole object but it usually crashes Carrara. The vertex modeler has a pretty steep learning curve but it is well worth the effort. Version 1.1 is just fixes the major bugs in version 1.0 which should have never been released. Carrara 2 is vastly superior to 1.1. And if you can afford it Version 3 is the way to go.