Error random while walking

Error occurred during application-update (11)
java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextNode(Unknown Source)
at java.util.HashMap$ValueIterator.next(Unknown Source)
at G.W.d(SourceFile:242)
at as.k.run(SourceFile:492)
at commons.JIWApplication.update(SourceFile:113)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.runLoop(LwjglAbstractDisplay.java:152)
at com.jme3.system.lwjgl.LwjglDisplay.runLoop(LwjglDisplay.java:192)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.run(LwjglAbstractDisplay.java:233)
at java.lang.Thread.run(Unknown Source)

OK thanks, that one was easy to grab with the debugger showing.