errors reading serialized JSlider

I got an error reading. Writing was fine:

com.thoughtworks.xstream.converters.ConversionException: Could not call javax.swing.event.EventListenerList.readObject()
---- Debugging information ----
required-type : javax.swing.event.EventListenerList
cause-message : null
class : music.LScore
message : Could not call javax.swing.event.EventListenerList.readObject()
line number : 352
path : /music.LScore/lparts/music.LPart/tc/first/sv/vg/javax.swing.JSlider/default/sliderModel/listenerList/javax.swing.event.EventListenerList/string
cause-exception : java.lang.reflect.InvocationTargetException
-------------------------------
at com.thoughtworks.xstream.converters.reflection.SerializationMethodInvoker.callReadObject(SerializationMethodInvoker.java:75)
at com.thoughtworks.xstream.converters.reflection.SerializableConverter.unmarshal(SerializableConverter.java:245)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:39)
at com.thoughtworks.xstream.core.ReferenceByXPathUnmarshaller.convertAnother(ReferenceByXPathUnmarshaller.java:37)
at com.thoughtworks.xstream.converters.reflection.ReflectionConverter.unmarshal(ReflectionConverter.java:105)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:39)
at com.thoughtworks.xstream.core.ReferenceByXPathUnmarshaller.convertAnother(ReferenceByXPathUnmarshaller.java:37)
at com.thoughtworks.xstream.converters.reflection.SerializableConverter$3.defaultReadObject(SerializableConverter.java:227)
at com.thoughtworks.xstream.converters.reflection.SerializableConverter.unmarshal(SerializableConverter.java:248)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:39)
at com.thoughtworks.xstream.core.ReferenceByXPathUnmarshaller.convertAnother(ReferenceByXPathUnmarshaller.java:37)
at com.thoughtworks.xstream.converters.reflection.ReflectionConverter.unmarshal(ReflectionConverter.java:105)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:39)
at com.thoughtworks.xstream.core.ReferenceByXPathUnmarshaller.convertAnother(ReferenceByXPathUnmarshaller.java:37)
at com.thoughtworks.xstream.converters.reflection.ReflectionConverter.unmarshal(ReflectionConverter.java:105)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:39)
at com.thoughtworks.xstream.core.ReferenceByXPathUnmarshaller.convertAnother(ReferenceByXPathUnmarshaller.java:37)
at com.thoughtworks.xstream.converters.reflection.ReflectionConverter.unmarshal(ReflectionConverter.java:105)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:39)
at com.thoughtworks.xstream.core.ReferenceByXPathUnmarshaller.convertAnother(ReferenceByXPathUnmarshaller.java:37)
at com.thoughtworks.xstream.converters.reflection.ReflectionConverter.unmarshal(ReflectionConverter.java:105)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:39)
at com.thoughtworks.xstream.core.ReferenceByXPathUnmarshaller.convertAnother(ReferenceByXPathUnmarshaller.java:37)
at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.readItem(AbstractCollectionConverter.java:58)
at com.thoughtworks.xstream.converters.collections.CollectionConverter.populateCollection(CollectionConverter.java:52)
at com.thoughtworks.xstream.converters.collections.CollectionConverter.unmarshal(CollectionConverter.java:45)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:39)
at com.thoughtworks.xstream.core.ReferenceByXPathUnmarshaller.convertAnother(ReferenceByXPathUnmarshaller.java:37)
at com.thoughtworks.xstream.converters.reflection.ReflectionConverter.unmarshal(ReflectionConverter.java:105)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:39)
at com.thoughtworks.xstream.core.ReferenceByXPathUnmarshaller.convertAnother(ReferenceByXPathUnmarshaller.java:37)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:96)
at com.thoughtworks.xstream.core.ReferenceByXPathMarshallingStrategy.unmarshal(ReferenceByXPathMarshallingStrategy.java:12)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:286)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:274)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:242)
at gui.PMGEditor.loadFile(PMGEditor.java:304)
at gui.PMGEditor.access$9(PMGEditor.java:276)
at gui.PMGEditor$5.actionPerformed(PMGEditor.java:172)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$ForwardActionEvents.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.AbstractButton.doClick(Unknown Source)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(Unknown Source)
at javax.swing.plaf.basic.BasicMenuItemUI$MouseInputHandler.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(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)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.thoughtworks.xstream.converters.reflection.SerializationMethodInvoker.callReadObject(SerializationMethodInvoker.java:71)
... 63 more
Caused by: com.thoughtworks.xstream.converters.ConversionException: Expected <default/> element in readObject() stream
---- Debugging information ----
-------------------------------
at com.thoughtworks.xstream.converters.reflection.SerializableConverter$3.defaultReadObject(SerializableConverter.java:213)
at com.thoughtworks.xstream.core.util.CustomObjectInputStream.defaultReadObject(CustomObjectInputStream.java:61)
at javax.swing.event.EventListenerList.readObject(Unknown Source)
... 68 more