in deploy/xxx-ds.xml, the dtd declaration requires an internet access :

starting jboss behind the firewall with the dtd declaration in my datasource ( Neo-ds.xml) I get :

(--> workaround after the stacktrace

15:59:47,565 ERROR [AbstractKernelController] Error installing to Parse: name=vfsfile:/C:/temp/downloads/jboss-5.0.0.CR1/jboss-5.0.0.CR1/server/default/deploy/Neo-ds.xml state=Not Installed mode=Manual requiredState=Parse
org.jboss.deployers.spi.DeploymentException: Error creating managed object for vfsfile:/C:/temp/downloads/jboss-5.0.0.CR1/jboss-5.0.0.CR1/server/default/deploy/Neo-ds.xml
at org.jboss.deployers.spi.DeploymentException.rethrowAsDeploymentException(DeploymentException.java:49)
at org.jboss.deployers.spi.deployer.helpers.AbstractParsingDeployerWithOutput.createMetaData(AbstractParsingDeployerWithOutput.java:343)
at org.jboss.deployers.spi.deployer.helpers.AbstractParsingDeployerWithOutput.createMetaData(AbstractParsingDeployerWithOutput.java:303)
at org.jboss.deployers.spi.deployer.helpers.AbstractParsingDeployerWithOutput.createMetaData(AbstractParsingDeployerWithOutput.java:275)
at org.jboss.deployers.spi.deployer.helpers.AbstractParsingDeployerWithOutput.deploy(AbstractParsingDeployerWithOutput.java:236)
at org.jboss.deployers.plugins.deployers.DeployerWrapper.deploy(DeployerWrapper.java:174)
at org.jboss.deployers.plugins.deployers.DeployersImpl.doInstallParentFirst(DeployersImpl.java:970)
at org.jboss.deployers.plugins.deployers.DeployersImpl.install(DeployersImpl.java:911)
at org.jboss.dependency.plugins.AbstractControllerContext.install(AbstractControllerContext.java:348)
at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:1392)
at org.jboss.dependency.plugins.AbstractController.incrementState(AbstractController.java:784)
at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:912)
at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:834)
at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:672)
at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:455)
at org.jboss.deployers.plugins.deployers.DeployersImpl.process(DeployersImpl.java:594)
at org.jboss.deployers.plugins.main.MainDeployerImpl.process(MainDeployerImpl.java:541)
at org.jboss.system.server.profileservice.ProfileServiceBootstrap.loadProfile(ProfileServiceBootstrap.java:257)
at org.jboss.system.server.profileservice.ProfileServiceBootstrap.start(ProfileServiceBootstrap.java:135)
at org.jboss.bootstrap.AbstractServerImpl.start(AbstractServerImpl.java:409)
at org.jboss.Main.boot(Main.java:209)
at org.jboss.Main$1.run(Main.java:544)
at java.lang.Thread.run(Thread.java:595)
Caused by: javax.xml.bind.UnmarshalException

• with linked exception:
  [java.net.SocketException: Network is unreachable: connect]
  at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:213)
  at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:190)
  at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:241)
  at org.jboss.resource.deployers.ManagedConnectionFactoryParserDeployer.parse(ManagedConnectionFactoryParserDeployer.java:132)
  at org.jboss.resource.deployers.ManagedConnectionFactoryParserDeployer.parse(ManagedConnectionFactoryParserDeployer.java:70)
  at org.jboss.deployers.vfs.spi.deployer.AbstractVFSParsingDeployer.parse(AbstractVFSParsingDeployer.java:185)
  at org.jboss.deployers.spi.deployer.helpers.AbstractParsingDeployerWithOutput.createMetaData(AbstractParsingDeployerWithOutput.java:336)
  ... 21 more
  Caused by: java.net.SocketException: Network is unreachable: connect
  at java.net.PlainSocketImpl.socketConnect(Native Method)
  at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
  at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
  at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
  at java.net.Socket.connect(Socket.java:520)
  at java.net.Socket.connect(Socket.java:470)
  at sun.net.NetworkClient.doConnect(NetworkClient.java:157)
  at sun.net.www.http.HttpClient.openServer(HttpClient.java:387)
  at sun.net.www.http.HttpClient.openServer(HttpClient.java:522)
  at sun.net.www.http.HttpClient.<init>(HttpClient.java:231)
  at sun.net.www.http.HttpClient.New(HttpClient.java:304)
  at sun.net.www.http.HttpClient.New(HttpClient.java:321)
  at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:813)
  at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:765)
  at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:690)
  at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:934)
  at org.apache.xerces.impl.XMLEntityManager.setupCurrentEntity(Unknown Source)
  at org.apache.xerces.impl.XMLEntityManager.startEntity(Unknown Source)
  at org.apache.xerces.impl.XMLEntityManager.startDTDEntity(Unknown Source)
  at org.apache.xerces.impl.XMLDTDScannerImpl.setInputSource(Unknown Source)
  at org.apache.xerces.impl.XMLDocumentScannerImpl$DTDDispatcher.dispatch(Unknown Source)
  at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
  at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
  at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
  at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
  at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
  at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
  at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:211)
  ... 27 more

WORKAROUND :

commenting the following dtd declaration in the datasource file solves the problem :
<!--
<!DOCTYPE datasources
PUBLIC "-//JBoss//DTD JBOSS JCA Config 1.5//EN"
"http://www.jboss.org/j2ee/dtd/jboss-ds_1_5.dtd">
-->

NOTE : my datasource file was generated by jboss tools ( new seam project)