I start the Scene Builder, select empty template then issue key combination meta + w and get the stack below.
This issue is mac specific.

Glass detected outstanding Java exception at -[GlassViewDelegate sendJavaKeyEvent:type:]:/HUDSON/workspace/2.0.2/label/macosx-universal-14/glass/glass-mat-lib-macosx/src/com/sun/mat/ui/GlassViewDelegate.m:280
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleKeyEvent(GlassViewEventHandler.java:125)
at com.sun.glass.ui.View.handleKeyEvent(View.java:248)
at com.sun.glass.ui.View.notifyKey(View.java:534)
Glass detected outstanding Java exception at -[GlassViewDelegate sendJavaKeyEvent:type:]:/HUDSON/workspace/2.0.2/label/macosx-universal-14/glass/glass-mat-lib-macosx/src/com/sun/mat/ui/GlassViewDelegate.m:292
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleKeyEvent(GlassViewEventHandler.java:125)
at com.sun.glass.ui.View.handleKeyEvent(View.java:248)
at com.sun.glass.ui.View.notifyKey(View.java:534)