unknown reference or circularity in instance dependences detected

Hi,

If I use MDR to process a parsered XML file, following error message 
will occur
What could be the reason?

Bin





javax.jmi.xmi.MalformedXMIException: 
org.netbeans.lib.jmi.util.DebugException: Unknown reference or 
circularity in instance dependences detected, bad reference: String
    at 
org.netbeans.lib.jmi.xmi.XMISaxReaderImpl.read(XMISaxReaderImpl.java:77)
    at 
org.netbeans.lib.jmi.xmi.XMISaxReaderImpl.read(XMISaxReaderImpl.java:59)
    at 
org.netbeans.modules.mdrexplorer.looks.reflect.actions.LoadXMIAction$1.run(LoadXMIAction.java:111)
    at org.openide.util.Task.run(Task.java:136)
    at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:328)
[catch] at 
org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:670)
==>
Annotation: XMI parsing error at line: 16685: Unknown reference or 
circularity in instance dependences detected, bad reference: String
org.netbeans.lib.jmi.util.DebugException: Unknown reference or 
circularity in instance dependences detected, bad reference: String
    at 
org.netbeans.lib.jmi.xmi.XmiSAXReader.endElement(XmiSAXReader.java:252)
    at org.apache.crimson.parser.Parser2.maybeElement(Parser2.java:1683)
    at org.apache.crimson.parser.Parser2.content(Parser2.java:1926)
    at org.apache.crimson.parser.Parser2.maybeElement(Parser2.java:1654)
    at org.apache.crimson.parser.Parser2.parseInternal(Parser2.java:634)
    at org.apache.crimson.parser.Parser2.parse(Parser2.java:333)
    at org.apache.crimson.parser.XMLReaderImpl.parse(XMLReaderImpl.java:448)
    at javax.xml.parsers.SAXParser.parse(SAXParser.java:345)
    at org.netbeans.lib.jmi.xmi.XmiSAXReader.read(XmiSAXReader.java:118)
    at org.netbeans.lib.jmi.xmi.XmiSAXReader.read(XmiSAXReader.java:99)
    at 
org.netbeans.lib.jmi.xmi.XMISaxReaderImpl.read(XMISaxReaderImpl.java:71)
    at 
org.netbeans.lib.jmi.xmi.XMISaxReaderImpl.read(XMISaxReaderImpl.java:59)
    at 
org.netbeans.modules.mdrexplorer.looks.reflect.actions.LoadXMIAction$1.run(LoadXMIAction.java:111)
    at org.openide.util.Task.run(Task.java:136)
    at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:328)
[catch] at 
org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:670)
==>
org.netbeans.lib.jmi.util.DebugException: Unknown reference or 
circularity in instance dependences detected, bad reference: String
    at 
org.netbeans.lib.jmi.xmi.XmiElement$Content.endElement(XmiElement.java:395)
    at 
org.netbeans.lib.jmi.xmi.XmiSAXReader.endElement(XmiSAXReader.java:240)
    at org.apache.crimson.parser.Parser2.maybeElement(Parser2.java:1683)
    at org.apache.crimson.parser.Parser2.content(Parser2.java:1926)
    at org.apache.crimson.parser.Parser2.maybeElement(Parser2.java:1654)
    at org.apache.crimson.parser.Parser2.parseInternal(Parser2.java:634)
    at org.apache.crimson.parser.Parser2.parse(Parser2.java:333)
    at org.apache.crimson.parser.XMLReaderImpl.parse(XMLReaderImpl.java:448)
    at javax.xml.parsers.SAXParser.parse(SAXParser.java:345)
    at org.netbeans.lib.jmi.xmi.XmiSAXReader.read(XmiSAXReader.java:118)
    at org.netbeans.lib.jmi.xmi.XmiSAXReader.read(XmiSAXReader.java:99)
    at 
org.netbeans.lib.jmi.xmi.XMISaxReaderImpl.read(XMISaxReaderImpl.java:71)
    at 
org.netbeans.lib.jmi.xmi.XMISaxReaderImpl.read(XMISaxReaderImpl.java:59)
    at 
org.netbeans.modules.mdrexplorer.looks.reflect.actions.LoadXMIAction$1.run(LoadXMIAction.java:111)
    at org.openide.util.Task.run(Task.java:136)
    at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:328)
[catch] at 
org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:670)
==>