Hi everybody. I am currently trying to upgrade an old app from JBoss 3.2.5 to the latest version in the hope of breathing some new life into it. I have made a number of changes suggested by the upgrade guide (changing my Datasource config etc.), however when I deploy my app am am getting some errors related apparently to xerces. I get this error if I try and deploy one web-app. 14:30:08,354 ERROR [Digester] Digester.getParser: java.lang.ClassCastException: org.apache.xerces.jaxp.SAXParserFactoryImpl at javax.xml.parsers.SAXParserFactory.newInstance(Unknown Source) I get this error when I try and access the other web-app (which seems to deploy ok). I have checked the org.apache.xerces.parsers.SAXParser class I am using and it definitely implements XMLReader). org.jdom.JDOMException: Could not load default SAX parser: org.apache.xerces.parsers.SAXParser: SAX2 driver class org.apache.xerces.parsers.SAXParser does not implement XMLReader I also have an ear which seems to deploy ok. I am using JBoss 4.0.5 and have recompiled everything against the xercesimpl.jar and xml-api.jar files found in JBoss's lib/endorsed folder. There are no other versions of xerces in any of my ears or wars - just that version. My initial research leads me to believe this is a class-loading issue and that maybe my default sax parser is incorrect? Anybody got any ideas? Thanks for your time. Robert Hughes