Decode the attached base64 encoded string and append to a text area will cause IllegalArgumentException on subsequent call to append. The decoded string probably has unregconized character encoding.

 Exception in thread "AWT-EventQueue-1" java.lang.IllegalArgumentException
    at sun.text.bidi.BidiBase.setLine(Unknown Source)
    at java.text.Bidi.createLineBidi(Unknown Source)
    at java.awt.font.TextMeasurer.makeTextLineOnRange(Unknown Source)
    at java.awt.font.TextMeasurer.getLayout(Unknown Source)
    at java.awt.font.LineBreakMeasurer.nextLayout(Unknown Source)
    at javax.swing.text.TextLayoutStrategy.sync(Unknown Source)
    at javax.swing.text.TextLayoutStrategy.insertUpdate(Unknown Source)
    at javax.swing.text.FlowView.loadChildren(Unknown Source)
    at javax.swing.text.CompositeView.setParent(Unknown Source)
    at javax.swing.text.FlowView.setParent(Unknown Source)
    at javax.swing.plaf.basic.BasicTextAreaUI$PlainParagraph.setParent(Unknown Source)
    at javax.swing.text.CompositeView.replace(Unknown Source)
    at javax.swing.text.BoxView.replace(Unknown Source)
    at javax.swing.text.CompositeView.loadChildren(Unknown Source)
    at javax.swing.text.CompositeView.setParent(Unknown Source)
    at javax.swing.plaf.basic.BasicTextUI$RootView.setView(Unknown Source)
    at javax.swing.plaf.basic.BasicTextUI.setView(Unknown Source)
    at javax.swing.plaf.basic.BasicTextUI.modelChanged(Unknown Source)
    at javax.swing.plaf.basic.BasicTextUI$UpdateHandler.insertUpdate(Unknown Source)
    at javax.swing.text.AbstractDocument.fireInsertUpdate(Unknown Source)
    at javax.swing.text.AbstractDocument.handleInsertString(Unknown Source)
    at javax.swing.text.AbstractDocument.insertString(Unknown Source)
    at javax.swing.text.PlainDocument.insertString(Unknown Source)
    at javax.swing.JTextArea.append(Unknown Source)
    at com.sun.deploy.uitoolkit.impl.awt.ui.SwingConsoleWindow$27.run(SwingConsoleWindow.java:531)
    at java.awt.event.InvocationEvent.dispatch(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)