The following exception is thrown when deploying a EAR archive containing a war and jar with the same name (except for the file extension, of course).
See https://community.jboss.org/thread/233648

2013-10-17 10:32:59,266 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-4) MSC000001: Failed to start service jboss.deployment.subunit."specj.ear"."specj.jar".POST_MODULE: org.jboss.msc.service.StartException in service jboss.deployment.subunit."specj.ear"."specj.jar".POST_MODULE: JBAS018733: Failed to process phase POST_MODULE of subdeployment "specj.jar" of deployment "specj.ear"
at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:166) [wildfly-server-8.0.0.Beta2-SNAPSHOT.jar:8.0.0.Beta2-SNAPSHOT]
at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1944) [jboss-msc-1.2.0.Beta2.jar:1.2.0.Beta2]
at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1877) [jboss-msc-1.2.0.Beta2.jar:1.2.0.Beta2]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [rt.jar:1.7.0_40]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [rt.jar:1.7.0_40]
at java.lang.Thread.run(Thread.java:724) [rt.jar:1.7.0_40]
Caused by: org.jboss.msc.service.DuplicateServiceException: Service jboss.concurrent.ee.context.config.specj.specj is already registered
at org.jboss.msc.service.ServiceRegistrationImpl.setInstance(ServiceRegistrationImpl.java:158) [jboss-msc-1.2.0.Beta2.jar:1.2.0.Beta2]
at org.jboss.msc.service.ServiceControllerImpl.startInstallation(ServiceControllerImpl.java:235) [jboss-msc-1.2.0.Beta2.jar:1.2.0.Beta2]
at org.jboss.msc.service.ServiceContainerImpl.install(ServiceContainerImpl.java:767) [jboss-msc-1.2.0.Beta2.jar:1.2.0.Beta2]
at org.jboss.msc.service.ServiceTargetImpl.install(ServiceTargetImpl.java:223) [jboss-msc-1.2.0.Beta2.jar:1.2.0.Beta2]
at org.jboss.msc.service.ServiceControllerImpl$ChildServiceTarget.install(ServiceControllerImpl.java:2384) [jboss-msc-1.2.0.Beta2.jar:1.2.0.Beta2]
at org.jboss.msc.service.ServiceTargetImpl.install(ServiceTargetImpl.java:223) [jboss-msc-1.2.0.Beta2.jar:1.2.0.Beta2]
at org.jboss.msc.service.ServiceControllerImpl$ChildServiceTarget.install(ServiceControllerImpl.java:2384) [jboss-msc-1.2.0.Beta2.jar:1.2.0.Beta2]
at org.jboss.msc.service.ServiceBuilderImpl.install(ServiceBuilderImpl.java:317) [jboss-msc-1.2.0.Beta2.jar:1.2.0.Beta2]
at org.jboss.as.ee.concurrent.deployers.EEConcurrentContextProcessor.setupConcurrentContext(EEConcurrentContextProcessor.java:110)
at org.jboss.as.ee.concurrent.deployers.EEConcurrentContextProcessor.processModuleDescription(EEConcurrentContextProcessor.java:71)
at org.jboss.as.ee.concurrent.deployers.EEConcurrentContextProcessor.deploy(EEConcurrentContextProcessor.java:54)
at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:159) [wildfly-server-8.0.0.Beta2-SNAPSHOT.jar:8.0.0.Beta2-SNAPSHOT]
... 5 more

2013-10-17 10:32:59,283 ERROR [org.jboss.as.controller.management-operation] (XNIO-1 task-3) JBAS014613: Operation ("deploy") failed - address: ([("deployment" => "specj.ear")]) - failure description: {
"JBAS014671: Failed services" =>

{"jboss.deployment.subunit.\"specj.ear\".\"specj.jar\".POST_MODULE" => "org.jboss.msc.service.StartException in service jboss.deployment.subunit.\"specj.ear\".\"specj.jar\".POST_MODULE: JBAS018733: Failed to process phase POST_MODULE of subdeployment \"specj.jar\" of deployment \"specj.ear\" Caused by: org.jboss.msc.service.DuplicateServiceException: Service jboss.concurrent.ee.context.config.specj.specj is already registered"}

,
"JBAS014771: Services with missing/unavailable dependencies" => ["jboss.deployment.unit.\"specj.ear\".weld.weldClassIntrospector is missing [jboss.deployment.unit.\"specj.ear\".beanmanager]"]
}