Many thanks, jaikiran, for your reply. Indeed the issue comes down to a missing librairy. I checked the link you gave, which was very helpful, but unfortunately I still failed to resolve the problem I tried several variants of the client's MANIFEST.MF a) Manifest-Version: 1.0 Class-Path: beans.jar jndi.properties %JBOSS_HOME%/jbossall-client.jar Main-Class: lemonpress.client.SimpleSessionClient b) Manifest-Version: 1.0 Class-Path: beans.jar jndi.properties C:/jboss/jbossall-client.jar Main-Class: lemonpress.client.SimpleSessionClient c) Manifest-Version: 1.0 Class-Path: beans.jar jndi.properties lib/jbossall-client.jar Main-Class: lemonpress.client.SimpleSessionClient (all fererenced files are physically at those locations and the new line added at the end of MANIFEST.MF) Yet, in all cases I am getting the deployment error: *** DEPLOYMENTS IN ERROR: Name -> Error vfsfile:/C:/jboss/server/default/deploy/simple_session.ear -> java.io.IOException: invalid manifest format -------------------------------------- more specifically: 22:14:17,015 WARN [VFSStructureBuilder] Error populating deployment vfsfile:/C:/jboss/server/default/deploy/simple_session.ear org.jboss.deployers.spi.DeploymentException: Error populating context vfsfile:/C:/jboss/server/default/deploy/simple_session.ear at org.jboss.deployers.spi.DeploymentException.rethrowAsDeploymentException(DeploymentException.java:49) at org.jboss.deployers.structure.spi.helpers.AbstractStructureBuilder.populateContext(AbstractStructureBuilder.java:144) at org.jboss.deployers.structure.spi.helpers.AbstractStructureBuilder.populateContext(AbstractStructureBuilder.java:83) at org.jboss.deployers.structure.spi.helpers.AbstractStructuralDeployers.determineStructure(AbstractStructuralDeployers.java:89) at org.jboss.deployers.plugins.main.MainDeployerImpl.determineStructure(MainDeployerImpl.java:743) at org.jboss.deployers.plugins.main.MainDeployerImpl.addDeployment(MainDeployerImpl.java:280) at org.jboss.deployers.plugins.main.MainDeployerImpl.addDeployment(MainDeployerImpl.java:237) at org.jboss.system.server.profileservice.ProfileServiceBootstrap.loadProfile(ProfileServiceBootstrap.java:244) at org.jboss.system.server.profileservice.ProfileServiceBootstrap.start(ProfileServiceBootstrap.java:131) ..... Caused by: java.io.IOException: invalid manifest format at java.util.jar.Manifest.read(Manifest.java:193) Would you be so kind to let me know what is wrong with my classpaths? ------------------------------------- Also when I add all 11 libraries to the classpath in the manifest I get a different kind of deployment error *** DEPLOYMENTS IN ERROR: Name -> Error vfsfile:/C:/jboss/server/default/deploy/simple_session.ear -> java.io.IOException: line too long This is worrying because assuming that my application grows I will probably need more libraries on the classpath Is there the way of circumventing this limitation? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4140283#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...