As described in 5070991, swing LayoutComparator used by LayoutFocusTraversalPolicy breaks the transitivity requirement.
In jdk7 b70 the mergesort algorithm has been modified (see 6804124). Now it may lead to IllegalArgumentException
as described on this forum thread:

http://forums.java.net/jive/thread.jspa?messageID=384566

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: Comparison method violates its general contract!
at java.util.TimSort.mergeHi(TimSort.java:868)
at java.util.TimSort.mergeAt(TimSort.java:485)
at java.util.TimSort.mergeForceCollapse(TimSort.java:426)
at java.util.TimSort.sort(TimSort.java:223)
at java.util.TimSort.sort(TimSort.java:173)
at java.util.Arrays.sort(Arrays.java:653)
at java.util.Collections.sort(Collections.java:217)
at javax.swing.SortingFocusTraversalPolicy.enumerateAndSortCycle(SortingFocusTraversalPolicy.java:136)
at javax.swing.SortingFocusTraversalPolicy.getFocusTraversalCycle(SortingFocusTraversalPolicy.java:110)
at javax.swing.SortingFocusTraversalPolicy.getFirstComponent(SortingFocusTraversalPolicy.java:435)
at javax.swing.LayoutFocusTraversalPolicy.getFirstComponent(LayoutFocusTraversalPolicy.java:166)
at javax.swing.SortingFocusTraversalPolicy.getDefaultComponent(SortingFocusTraversalPolicy.java:515)
at javax.swing.JComponent.requestDefaultFocus(JComponent.java:2618)
at sun.swing.SwingUtilities2.tabbedPaneChangeFocusTo(SwingUtilities2.java:1566)
at javax.swing.JTabbedPane.fireStateChanged(JTabbedPane.java:398)
at javax.swing.JTabbedPane$ModelListener.stateChanged(JTabbedPane.java:270)
at javax.swing.DefaultSingleSelectionModel.fireStateChanged(DefaultSingleSelectionModel.java:132)
at javax.swing.DefaultSingleSelectionModel.setSelectedIndex(DefaultSingleSelectionModel.java:67)
at javax.swing.JTabbedPane.setSelectedIndexImpl(JTabbedPane.java:616)
at javax.swing.JTabbedPane.setSelectedIndex(JTabbedPane.java:591)
at javax.swing.plaf.basic.BasicTabbedPaneUI$Handler.mousePressed(BasicTabbedPaneUI.java:3637)
at java.awt.Component.processMouseEvent(Component.java:6427)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6195)
at java.awt.Container.processEvent(Container.java:2203)
at java.awt.Component.dispatchEventImpl(Component.java:4790)
at java.awt.Container.dispatchEventImpl(Container.java:2261)
at java.awt.Component.dispatchEvent(Component.java:4616)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4800)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4460)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4393)
at java.awt.Container.dispatchEventImpl(Container.java:2247)
at java.awt.Window.dispatchEventImpl(Window.java:2671)
at java.awt.Component.dispatchEvent(Component.java:4616)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:651)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:255)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:170)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:160)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:155)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:136)