Recent wildfly-8.0.0.Beta1-SNAPSHOT (IronJacamar 1.1.0.Final) throws following error intermittently when there are multiple RARs in an EAR:
13:12:34,710 ERROR [org.jboss.msc.service] (MSC service thread 1-10) MSC000002: Invocation of listener "org.jboss.as.connector.deployers.ra.processors.ParsedRaDeploymentProcessor$1@e7b3aee" failed: java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:894) [rt.jar:1.7.0_25]
at java.util.HashMap$KeyIterator.next(HashMap.java:928) [rt.jar:1.7.0_25]
at org.jboss.as.connector.subsystems.resourceadapters.IronJacamarResourceCreator.getIronJacamarResource(IronJacamarResourceCreator.java:335) [wildfly-connector-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.connector.subsystems.resourceadapters.IronJacamarResourceCreator.execute(IronJacamarResourceCreator.java:350) [wildfly-connector-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.connector.deployers.ra.processors.ParsedRaDeploymentProcessor$1.registerIronjacamar(ParsedRaDeploymentProcessor.java:145) [wildfly-connector-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.connector.deployers.ra.processors.AbstractResourceAdapterDeploymentServiceListener.transition(AbstractResourceAdapterDeploymentServiceListener.java:244) [wildfly-connector-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.msc.service.ServiceControllerImpl.invokeListener(ServiceControllerImpl.java:1533) [jboss-msc-1.2.0.Beta2.jar:1.2.0.Beta2]
at org.jboss.msc.service.ServiceControllerImpl.access$2800(ServiceControllerImpl.java:51) [jboss-msc-1.2.0.Beta2.jar:1.2.0.Beta2]
at org.jboss.msc.service.ServiceControllerImpl$ListenerTask.run(ServiceControllerImpl.java:2095) [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_25]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [rt.jar:1.7.0_25]
at java.lang.Thread.run(Thread.java:724) [rt.jar:1.7.0_25]

Older versions had a similar problem as detailed in JBJCA-933 (which also shows interleaving example with 3 RARs).