From a similar question of the FAQ http://www.sweethome3d.eu/faq.html#errorIn3DRenderingSystem , you should try the version that works with Java 3D 1.3 available at http://www.sweethome3d.eu/SweetHome3D-Java3D1.3.jnlp

I don't know if will fix your problem, but I'll be pleased to know.