I restarted the computer (since it had gone through an Arch-linux continuous update recently, I suspected that the potentially updated drivers may need the restart to kick in. ) Then it worked. (Though I see 3d view only in the main window and not in a separate window.)
I have the same problem (2 monitors connected to a arch linux desktop): /opt/SweetHome3D-6.2/SweetHome3D-Java3D-1_5_2 Java 3D: implicit antialiasing enabled Exception in thread "AWT-EventQueue-0" javax.media.j3d.IllegalRenderingStateException: Can't create graphics environment for Canvas 3D at com.eteks.sweethome3d.j3d.Component3DManager.getCanvas3D(Unknown Source) at com.eteks.sweethome3d.j3d.Component3DManager.getOnscreenCanvas3D(Unknown Source) at com.eteks.sweethome3d.swing.HomeComponent3D.createComponent3D(Unknown...