I got this exception on application server startup, however it is not reproducible so it is probably some kind of race condition within MSC.

08:27:27,666 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-10) MSC00001: Failed to start service jboss.deployment.subunit."jboss-seam-numberguess.ear"."jboss-seam-numberguess.jar".STRUCTURE: org.jboss.msc.service.StartException in service jboss.deployment.subunit."jboss-seam-numberguess.ear"."jboss-seam-numberguess.jar".STRUCTURE: Failed to start service
at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1696) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) [:1.6.0_22]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) [:1.6.0_22]
at java.lang.Thread.run(Thread.java:680) [:1.6.0_22]
Caused by: java.lang.NullPointerException
at org.jboss.msc.service.ServiceTargetImpl.install(ServiceTargetImpl.java:188) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
at org.jboss.msc.service.ServiceControllerImpl$ChildServiceTarget.install(ServiceControllerImpl.java:2165) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
at org.jboss.msc.service.ServiceTargetImpl.install(ServiceTargetImpl.java:188) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
at org.jboss.msc.service.ServiceControllerImpl$ChildServiceTarget.install(ServiceControllerImpl.java:2165) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
at org.jboss.msc.service.ServiceBuilderImpl.install(ServiceBuilderImpl.java:325) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:152) [jboss-as-server-7.0.0.Beta4-SNAPSHOT.jar:7.0.0.Beta4-SNAPSHOT]
at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1675) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
... 3 more

08:27:27,666 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-4) MSC00001: Failed to start service jboss.deployment.subunit."jboss-seam-numberguess.ear"."jboss-seam.jar".STRUCTURE: org.jboss.msc.service.StartException in service jboss.deployment.subunit."jboss-seam-numberguess.ear"."jboss-seam.jar".STRUCTURE: Failed to start service
at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1696) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) [:1.6.0_22]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) [:1.6.0_22]
at java.lang.Thread.run(Thread.java:680) [:1.6.0_22]
Caused by: java.lang.NullPointerException
at org.jboss.msc.service.ServiceTargetImpl.install(ServiceTargetImpl.java:188) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
at org.jboss.msc.service.ServiceControllerImpl$ChildServiceTarget.install(ServiceControllerImpl.java:2165) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
at org.jboss.msc.service.ServiceTargetImpl.install(ServiceTargetImpl.java:188) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
at org.jboss.msc.service.ServiceControllerImpl$ChildServiceTarget.install(ServiceControllerImpl.java:2165) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
at org.jboss.msc.service.ServiceBuilderImpl.install(ServiceBuilderImpl.java:325) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:152) [jboss-as-server-7.0.0.Beta4-SNAPSHOT.jar:7.0.0.Beta4-SNAPSHOT]
at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1675) [jboss-msc-1.0.0.Beta8.jar:1.0.0.Beta8]
... 3 more