I have a silhouette cameo and the basic software doesn't open svgs. I am bringing in my files, tracing in inkscape and saving as dxf. everything looks great. However when I take back to silhouette studio it all goes wrong with extra lines etc Any ideas why?

There are several topics here with dxf converting issues.
Have you tried to use pdf instead? Seems to work better some cases.
http://www.inkscapeforum.com/viewtopic.php?f=31&t=6003&p=59185#p59185