The application is a war file and reads EDI files and applies these as updates to the database. There are few html pages where you can 'take the temperature' of the application, and it is on these pages that the error occurrs. One difference between Jboss 3.2.2 and jboss 4.2.1 is the use of Avalon framework. This is in 4.2.1 placed in lib directory whereas it was not present in 3.2.2. Since Cocoon uses Avalon framework I had to use isolation(http://wiki.jboss.org/wiki/Wiki.jsp?page=ClassLoadingConfiguration, updated jboss-web.xml and this made the application run as it should in deploy directory under 4.2.1. Here are the scenarios I have tried. All have been deployed in deploy-hasingleton 1) Put the war file in deploy-hasingleton, as it is described in the Jboss Clustering Guide. The error occurred and this is shown in the log Only the root deployment can set the loader repository, ignoring config=LoaderRepositoryConfig(repositoryName: jboss.dataintegration:war=dataintegration.war, repositoryClassName: org.jboss.mx.loading.HeirarchicalLoaderRepository3, configParserClassName: org.jboss.mx.loading.HeirarchicalLoaderRepository3ConfigParser, repositoryConfig: java2ParentDelegation=false) but according to 'http://wiki.jboss.org/wiki/Wiki.jsp?page=GetWARNquotOnlyTheRootDeploymentCanSetTheLoaderRepositoryquotOn3.2.5', this can be ignored 2) Created a SAR and a jboss-service.xml with isolation and and an mbean containing HASingletonController. The same error occurred, but again this is shown in the log Only the root deployment can set the loader repository, ignoring config=LoaderRepositoryConfig(repositoryName: jboss.dataintegration:sar=dataintegration.sar, repositoryClassName: org.jboss.mx.loading.HeirarchicalLoaderRepository3, configParserClassName: org.jboss.mx.loading.HeirarchicalLoaderRepository3ConfigParser, repositoryConfig: java2ParentDelegation=false) for both sar and war 3) Created a SAR and a jboss-service.xml with isolation and and an mbean containing HASingletonController but this time the isolation in jboss-web.xml in the war file is removed. The same error occurred, but again this is shown in the log: Only the root deployment can set the loader repository, ignoring config=LoaderRepositoryConfig(repositoryName: jboss.dataintegration:sar=dataintegration.sar, repositoryClassName: org.jboss.mx.loading.HeirarchicalLoaderRepository3, configParserClassName: org.jboss.mx.loading.HeirarchicalLoaderRepository3ConfigParser, repositoryConfig: java2ParentDelegation=false) I think it is odd that each time the application is deployed in deploy-hasingleton and fails, the text about root deployment that can be ignored, is showing. I used to think that this problem wa related to classpath, but I am not so sure Lasse Petersen View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4132416#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...