Hadoop application hangs due to container token and NM token error

i'm new to Hadoop developing and i'm trying to install a multi-node cluster on Hadoop 2.4.1. However, i'm going through some issues. When i try to execute an example (wordcount or pi), the execution stops at

INFO mapreduce.Job: Running job: job_1412689235580_0001

and analyzing the logs i get a repeted error in the resourcemanager log:

     2014-10-07 15:56:40,978 ERROR org.apache.hadoop.yarn.server.resourcemanager.scheduler.SchedulerApplicationAttempt: Error trying to assign container token and NM token to an allocated container container_1412689235580_0001_01_000001
java.lang.IllegalArgumentException: java.net.UnknownHostException: federica-VirtualBox
at org.apache.hadoop.security.SecurityUtil.buildTokenService(SecurityUtil.java:377)
at org.apache.hadoop.yarn.server.utils.BuilderUtils.newContainerToken(BuilderUtils.java:248)
at org.apache.hadoop.yarn.server.resourcemanager.security.RMContainerTokenSecretManager.createContainerToken(RMContainerTokenSecretManager.java:195)
at org.apache.hadoop.yarn.server.resourcemanager.scheduler.SchedulerApplicationAttempt.pullNewlyAllocatedContainersAndNMTokens(SchedulerApplicationAttempt.java:379)
at org.apache.hadoop.yarn.server.resourcemanager.scheduler.common.fica.FiCaSchedulerApp.getAllocation(FiCaSchedulerApp.java:240)
at org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.CapacityScheduler.allocate(CapacityScheduler.java:716)
at org.apache.hadoop.yarn.server.resourcemanager.rmapp.attempt.RMAppAttemptImpl$AMContainerAllocatedTransition.transition(RMAppAttemptImpl.java:821)
at org.apache.hadoop.yarn.server.resourcemanager.rmapp.attempt.RMAppAttemptImpl$AMContainerAllocatedTransition.transition(RMAppAttemptImpl.java:814)
at org.apache.hadoop.yarn.state.StateMachineFactory$MultipleInternalArc.doTransition(StateMachineFactory.java:385)
at org.apache.hadoop.yarn.state.StateMachineFactory.doTransition(StateMachineFactory.java:302)
at org.apache.hadoop.yarn.state.StateMachineFactory.access$300(StateMachineFactory.java:46)
at org.apache.hadoop.yarn.state.StateMachineFactory$InternalStateMachine.doTransition(StateMachineFactory.java:448)
at org.apache.hadoop.yarn.server.resourcemanager.rmapp.attempt.RMAppAttemptImpl.handle(RMAppAttemptImpl.java:652)
at org.apache.hadoop.yarn.server.resourcemanager.rmapp.attempt.RMAppAttemptImpl.handle(RMAppAttemptImpl.java:106)
at org.apache.hadoop.yarn.server.resourcemanager.ResourceManager$ApplicationAttemptEventDispatcher.handle(ResourceManager.java:753)
at org.apache.hadoop.yarn.server.resourcemanager.ResourceManager$ApplicationAttemptEventDispatcher.handle(ResourceManager.java:734)
at org.apache.hadoop.yarn.event.AsyncDispatcher.dispatch(AsyncDispatcher.java:173)
at org.apache.hadoop.yarn.event.AsyncDispatcher$1.run(AsyncDispatcher.java:106)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.UnknownHostException: federica-VirtualBox
... 19 more

Does anyone know what this means and how can i fix it? Thanks

Davide