I recently ran across a problem with the Embedded Glassfish 4 maven problem.. as soon as I tried to activate any CDI specific stuff, I got the following exception:

Sep 08, 2013 11:05:37 PM org.glassfish.deployment.admin.DeployCommand execute
SEVERE: Exception while loading the app : CDI deployment failure:WELD-001524 Unable to load proxy class for bean Implicit Bean [javax.enterprise.inject.Instance] with qualifiers [@Default] with class interface javax.enterprise.inject.Instance using classloader WebappClassLoader (delegate=true; repositories=WEB-INF/classes/)
org.jboss.weld.exceptions.WeldException: WELD-001524 Unable to load proxy class for bean Implicit Bean [javax.enterprise.inject.Instance] with qualifiers [@Default] with class interface javax.enterprise.inject.Instance using classloader WebappClassLoader (delegate=true; repositories=WEB-INF/classes/)
at org.jboss.weld.bean.proxy.ProxyFactory.getProxyClass(ProxyFactory.java:306)
at org.jboss.weld.bean.builtin.AbstractFacadeBean.initializeAfterBeanDiscovery(AbstractFacadeBean.java:60)
at org.jboss.weld.bootstrap.BeanDeployer.doAfterBeanDiscovery(BeanDeployer.java:354)
at org.jboss.weld.bootstrap.BeanDeployment.afterBeanDiscovery(BeanDeployment.java:280)
at org.jboss.weld.bootstrap.WeldBootstrap.deployBeans(WeldBootstrap.java:522)
at org.glassfish.weld.WeldDeployer.event(WeldDeployer.java:213)
at org.glassfish.kernel.event.EventsImpl.send(EventsImpl.java:131)
at org.glassfish.internal.data.ApplicationInfo.load(ApplicationInfo.java:328)
at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:493)
at com.sun.enterprise.v3.server.ApplicationLifecycle.deploy(ApplicationLifecycle.java:219)
at org.glassfish.deployment.admin.DeployCommand.execute(DeployCommand.java:491)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:527)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$2$1.run(CommandRunnerImpl.java:523)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:356)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$2.execute(CommandRunnerImpl.java:522)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:546)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.doCommand(CommandRunnerImpl.java:1423)
at com.sun.enterprise.v3.admin.CommandRunnerImpl.access$1500(CommandRunnerImpl.java:108)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1762)
at com.sun.enterprise.v3.admin.CommandRunnerImpl$ExecutionContext.execute(CommandRunnerImpl.java:1674)
at com.sun.enterprise.admin.cli.embeddable.DeployerImpl.deploy(DeployerImpl.java:133)
at com.sun.enterprise.admin.cli.embeddable.DeployerImpl.deploy(DeployerImpl.java:109)
at org.glassfish.maven.PluginUtil.doDeploy(PluginUtil.java:106)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.glassfish.maven.AbstractDeployMojo.doDeploy(AbstractDeployMojo.java:239)
at org.glassfish.maven.RunMojo.execute(RunMojo.java:68)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:106)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:318)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:153)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:555)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:214)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:158)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:414)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:357)
Caused by: java.lang.LinkageError: loader constraint violation: loader (instance of org/codehaus/plexus/classworlds/realm/ClassRealm) previously initiated loading for a different type with name "javax/enterprise/util/TypeLiteral"
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:792)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClassFromSelf(ClassRealm.java:386)
at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(SelfFirstStrategy.java:42)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:244)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:230)
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2521)
at java.lang.Class.privateGetPublicMethods(Class.java:2641)
at java.lang.Class.getMethods(Class.java:1457)
at org.jboss.weld.bean.proxy.ProxyFactory.addMethodsFromClass(ProxyFactory.java:513)
at org.jboss.weld.bean.proxy.ProxyFactory.addMethods(ProxyFactory.java:468)
at org.jboss.weld.bean.proxy.ProxyFactory.createProxyClass(ProxyFactory.java:402)
at org.jboss.weld.bean.proxy.ProxyFactory.getProxyClass(ProxyFactory.java:299)
... 50 more

Sep 08, 2013 11:05:37 PM PluginUtil doDeploy
INFO: Deployed null

As it turned out, this is a problem with Maven 3.1 which now bundles Plexus without correctly isolating the classpath.
If you have this problem as well, use Maven 3.0.5 instead.

This issue is reported on the Glassfish JIRA.