NullPointer exception when deploying WAR file

Migrating from 4.2.3 to 5.1.0. When deploying a specific WAR file (recompiled against jdk 6) in 5.1.0.GA I get the following exception:

12:03:47,949 ERROR [AbstractKernelController] Error installing to PostClassLoader: name=vfszip:/opt/jboss-5.1.0.GA/server/trp/deploy/certification-war-0.7-SNAPSHOT-development.war/ state=ClassLoader mode=Manual requiredState=PostClassLoader
org.jboss.deployers.spi.DeploymentException: Error during deploy: vfszip:/opt/jboss-5.1.0.GA/server/trp/deploy/certification-war-0.7-SNAPSHOT-development.war/
at org.jboss.deployers.spi.DeploymentException.rethrowAsDeploymentException(DeploymentException.java:49)
at org.jboss.deployers.plugins.deployers.DeployerWrapper.deploy(DeployerWrapper.java:177)
at org.jboss.deployers.plugins.deployers.DeployersImpl.doDeploy(DeployersImpl.java:1439)
at org.jboss.deployers.plugins.deployers.DeployersImpl.doInstallParentFirst(DeployersImpl.java:1157)
at org.jboss.deployers.plugins.deployers.DeployersImpl.install(DeployersImpl.java:1098)
at org.jboss.dependency.plugins.AbstractControllerContext.install(AbstractControllerContext.java:348)
at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:1631)
at org.jboss.dependency.plugins.AbstractController.incrementState(AbstractController.java:934)
at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:1082)
at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:984)
at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:822)
at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:553)
at org.jboss.deployers.plugins.deployers.DeployersImpl.process(DeployersImpl.java:781)
at org.jboss.deployers.plugins.main.MainDeployerImpl.process(MainDeployerImpl.java:702)
at org.jboss.system.server.profileservice.repository.MainDeployerAdapter.process(MainDeployerAdapter.java:117)
at org.jboss.system.server.profileservice.hotdeploy.HDScanner.scan(HDScanner.java:362)
at org.jboss.system.server.profileservice.hotdeploy.HDScanner.run(HDScanner.java:255)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:317)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:150)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:98)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.runPeriodic(ScheduledThreadPoolExecutor.java:181)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:205)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NullPointerException
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at org.jboss.metadata.process.processor.ejb.jboss.SetDefaultLocalBusinessInterfaceProcessor.process(SetDefaultLocalBusinessInterfaceProcessor.java:114)
at org.jboss.metadata.process.chain.ejb.jboss.JBossMetaDataProcessorChain.process(JBossMetaDataProcessorChain.java:115)
at org.jboss.ejb3.deployers.Ejb3MetadataProcessingDeployer.deploy(Ejb3MetadataProcessingDeployer.java:115)
at org.jboss.deployers.plugins.deployers.DeployerWrapper.deploy(DeployerWrapper.java:171)
... 24 more
12:03:47,997 WARN [HDScanner] Failed to process changes
org.jboss.deployers.client.spi.IncompleteDeploymentException: Summary of incomplete deployments (SEE PREVIOUS ERRORS FOR DETAILS):

• • • DEPLOYMENTS IN ERROR: Name -> Error

vfszip:/opt/jboss-5.1.0.GA/server/trp/deploy/certification-war-0.7-SNAPSHOT-development.war/ -> org.jboss.deployers.spi.DeploymentException: Error during deploy: vfszip:/opt/jboss-5.1.0.GA/server/trp/deploy/certification-war-0.7-SNAPSHOT-development.war/

The corresponding JBoss web:

<?xml version="1.0" encoding="UTF-8"?>
<jboss-web xmlns:xs="http://www.jboss.org/j2ee/schema"
xs:schemaLocation="http://www.jboss.org/j2ee/schema http://www.jboss.org/j2ee/schema/jboss-web_5_1.xsd"
version="5.1">
<class-loading>
<loader-repository>net.ripe:loader=certification-war.war</loader-repository>
</class-loading>
<security-domain>java:/jaas/rpki</security-domain>

<context-root>certification</context-root>
</jboss-web>

The WAR file uses some remote EJB's that are deployed succesfully.

I downloaded the JBoss source code to investigate some more but the class org.jboss.metadata.process.processor.ejb.jboss.SetDefaultLocalBusinessInterfaceProcessor is not in the downloaded jboss-5.1.0.GA-src.tar.gz.

Any thoughts how to proceed?