I'm seeing an odd problem when deploying a Seam EAR to JBoss 4.2.2. I get the following exception:

11:03:05,109 ERROR [[/public]] Exception sending context initialized event to listener instance of class org.jboss.seam.servlet.SeamListener
java.lang.ClassFormatError: Illegal class modifiers in class org/jboss/seam/async/package-info: 0x1600
 at java.lang.ClassLoader.defineClass1(Native Method)
 at java.lang.ClassLoader.defineClass(ClassLoader.java:675)
 at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
 at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1814)
 at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:872)
 at org.jboss.web.tomcat.service.WebAppClassLoader.findClass(WebAppClassLoader.java:139)
 at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1325)
 at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1204)
 at org.jboss.seam.deployment.NamespaceDeploymentHandler.getPackage(NamespaceDeploymentHandler.java:69)
 at org.jboss.seam.deployment.NamespaceDeploymentHandler.handle(NamespaceDeploymentHandler.java:44)
 at org.jboss.seam.deployment.DeploymentStrategy.handle(DeploymentStrategy.java:81)
 at org.jboss.seam.deployment.AbstractScanner.handleItem(AbstractScanner.java:30)
 at org.jboss.seam.deployment.URLScanner.handleArchiveByFile(URLScanner.java:117)
 at org.jboss.seam.deployment.URLScanner.handle(URLScanner.java:98)
 at org.jboss.seam.deployment.URLScanner.scanResources(URLScanner.java:81)
 at org.jboss.seam.deployment.StandardDeploymentStrategy.scan(StandardDeploymentStrategy.java:67)
 at org.jboss.seam.init.Initialization.create(Initialization.java:102)
 at org.jboss.seam.servlet.SeamListener.contextInitialized(SeamListener.java:34)
 at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3856)
 at org.apache.catalina.core.StandardContext.start(StandardContext.java:4361)
 at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:790)
 at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:770)
 at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:553)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:296)
 at org.jboss.mx.server.RawDynamicInvoker.invoke(RawDynamicInvoker.java:164)
 at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:659)
 at org.apache.catalina.core.StandardContext.init(StandardContext.java:5312)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:296)
 at org.jboss.mx.server.RawDynamicInvoker.invoke(RawDynamicInvoker.java:164)
 at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:659)
 at org.jboss.web.tomcat.service.TomcatDeployer.performDeployInternal(TomcatDeployer.java:301)
 at org.jboss.web.tomcat.service.TomcatDeployer.performDeploy(TomcatDeployer.java:104)
 at org.jboss.web.AbstractWebDeployer.start(AbstractWebDeployer.java:375)
 at org.jboss.web.WebModule.startModule(WebModule.java:83)
 at org.jboss.web.WebModule.startService(WebModule.java:61)
 at org.jboss.system.ServiceMBeanSupport.jbossInternalStart(ServiceMBeanSupport.java:289)
 at org.jboss.system.ServiceMBeanSupport.jbossInternalLifecycle(ServiceMBeanSupport.java:245)
 at sun.reflect.GeneratedMethodAccessor3.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatcher.java:155)
 at org.jboss.mx.server.Invocation.dispatch(Invocation.java:94)
 at org.jboss.mx.server.Invocation.invoke(Invocation.java:86)
 at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:264)
 at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:659)
 at org.jboss.system.ServiceController$ServiceProxy.invoke(ServiceController.java:978)
 at $Proxy0.start(Unknown Source)
 at org.jboss.system.ServiceController.start(ServiceController.java:417)
 at sun.reflect.GeneratedMethodAccessor9.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatcher.java:155)
 at org.jboss.mx.server.Invocation.dispatch(Invocation.java:94)
 at org.jboss.mx.server.Invocation.invoke(Invocation.java:86)
 at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:264)
 at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:659)
 at org.jboss.mx.util.MBeanProxyExt.invoke(MBeanProxyExt.java:210)
 at $Proxy44.start(Unknown Source)
 at org.jboss.web.AbstractWebContainer.start(AbstractWebContainer.java:466)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatcher.java:155)
 at org.jboss.mx.server.Invocation.dispatch(Invocation.java:94)
 at org.jboss.mx.interceptor.AbstractInterceptor.invoke(AbstractInterceptor.java:133)
 at org.jboss.mx.server.Invocation.invoke(Invocation.java:88)
 at org.jboss.mx.interceptor.ModelMBeanOperationInterceptor.invoke(ModelMBeanOperationInterceptor.java:142)
 at org.jboss.mx.interceptor.DynamicInterceptor.invoke(DynamicInterceptor.java:97)
 at org.jboss.system.InterceptorServiceMBeanSupport.invokeNext(InterceptorServiceMBeanSupport.java:238)
 at org.jboss.wsf.container.jboss42.DeployerInterceptor.start(DeployerInterceptor.java:87)
 at org.jboss.deployment.SubDeployerInterceptorSupport$XMBeanInterceptor.start(SubDeployerInterceptorSupport.java:188)
 at org.jboss.deployment.SubDeployerInterceptor.invoke(SubDeployerInterceptor.java:95)
 at org.jboss.mx.server.Invocation.invoke(Invocation.java:88)
 at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:264)
 at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:659)
 at org.jboss.mx.util.MBeanProxyExt.invoke(MBeanProxyExt.java:210)
 at $Proxy45.start(Unknown Source)
 at org.jboss.deployment.MainDeployer.start(MainDeployer.java:1025)
 at org.jboss.deployment.MainDeployer.start(MainDeployer.java:1015)
 at org.jboss.deployment.MainDeployer.deploy(MainDeployer.java:819)
 at org.jboss.deployment.MainDeployer.deploy(MainDeployer.java:782)
 at sun.reflect.GeneratedMethodAccessor20.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatcher.java:155)
 at org.jboss.mx.server.Invocation.dispatch(Invocation.java:94)
 at org.jboss.mx.interceptor.AbstractInterceptor.invoke(AbstractInterceptor.java:133)
 at org.jboss.mx.server.Invocation.invoke(Invocation.java:88)
 at org.jboss.mx.interceptor.ModelMBeanOperationInterceptor.invoke(ModelMBeanOperationInterceptor.java:142)
 at org.jboss.mx.server.Invocation.invoke(Invocation.java:88)
 at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:264)
 at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:659)
 at org.jboss.mx.util.MBeanProxyExt.invoke(MBeanProxyExt.java:210)
 at $Proxy9.deploy(Unknown Source)
 at org.jboss.deployment.scanner.URLDeploymentScanner.deploy(URLDeploymentScanner.java:421)
 at org.jboss.deployment.scanner.URLDeploymentScanner.scan(URLDeploymentScanner.java:610)
 at org.jboss.deployment.scanner.AbstractDeploymentScanner$ScannerThread.doScan(AbstractDeploymentScanner.java:263)
 at org.jboss.deployment.scanner.AbstractDeploymentScanner$ScannerThread.loop(AbstractDeploymentScanner.java:274)
 at org.jboss.deployment.scanner.AbstractDeploymentScanner$ScannerThread.run(AbstractDeploymentScanner.java:225)
11:03:05,113 ERROR [StandardContext] Error listenerStart
11:03:05,113 ERROR [StandardContext] Context [/public] startup failed due to previous errors

I noticed this yesterday briefly when my SeamTests started throwing the same exception, except the problem went away after Maven grabbed the new snapshots (of either Seam or JBoss Embedded, I'm not sure which).

Any ideas.