In the SwingInterop demo, select some text in a web page in the Web Browser tab and the following exception is thrown:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at javafx.embed.swing.SwingDnD$2.dragDropEnd(SwingDnD.java:119)

Subsequent attempts to drag and drop text also result in a second exception:

java.lang.IllegalArgumentException: Key already associated with a running event loop: java.lang.Object@37e02b65
        at com.sun.javafx.tk.quantum.QuantumToolkit.enterNestedEventLoop(QuantumToolkit.java:514)

See the attached file for the complete exceptions.

The issue I filed at RT-24664 is similar.