いつもお世話になっております.

Protocol Designerで作成し, 保存した.pdnファイルですが,
QualNetを一旦終了し, 再び起動させたところ, 開けなくなりました.
開いてもキャンパスには状態遷移図が出て来ません.

どうしたらよいのでしょうか？
また, 何が原因でしょうか？

ide.logには以下のようなものが出ます. -------------------

java.lang.NullPointerException
at java.lang.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:980)
at java.lang.Double.parseDouble(Double.java:220)
at com.snt.protocol.designer.StateModel.setAttributes(StateModel.java:982)
at com.snt.protocol.designer.StateModel.open(StateModel.java:963)
at com.snt.protocol.designer.States.open(States.java:128)
at com.snt.protocol.designer.CanvasModel.setChildren(CanvasModel.java:350)
at com.snt.protocol.designer.CanvasModel.open(CanvasModel.java:318)
at com.snt.protocol.designer.ProtocolModel.setChildren(ProtocolModel.java:293)
at com.snt.protocol.designer.ProtocolModel.protocolLoad(ProtocolModel.java:212)
at com.snt.protocol.loaders.ProtocolEditorSupport.loadProtocolImpl(ProtocolEditorSupport.java:180)
at com.snt.protocol.loaders.ProtocolEditorSupport$2.run(ProtocolEditorSupport.java:228)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:178)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:454)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)