b12 seems to have broken my custom control that I imported with a JAR file. Since my control creates its own CSS metadata, it accesses converters in com.sun.javafx.css.convrrters. Scenebuilder barfs on this with an access denied exception:

Caused by: java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "accessClassInPackage.com.sun.javafx.css.converters")
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:457)
at java.security.AccessController.checkPermission(AccessController.java:884)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
at java.lang.SecurityManager.checkPackageAccess(SecurityManager.java:1564)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:305)
at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at com.stanfordcomputing.datumo.gui.control.symbol.SVGView$StyleableProperties.<clinit>(SVGView.java:161)