When closing a transaction the DefaultSeamTransaction.getUserTransaction() looks up the transaction using the comp namespace. This fails when using AS7. This only appears to occur when the transaction is rolled back with a persistence error from the datasource; in this case a not null constraint was violated. I guess regardless of the cause it is looking up the transaction from java:comp which seems to no longer be supported. The application will persist fine under normal circumstances when using 3.0.1.SNAPSHOT.

Error stack is as follows:
ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[default-host]] (http--127.0.0.1-8080-7) Exception sending request destroyed lifecycle event to listener instance of class org.jboss.weld.servlet.WeldListener: java.lang.RuntimeException: javax.naming.NamingException: Failed to get context with name comp
at org.jboss.seam.transaction.DefaultSeamTransaction.getSeamTransaction(DefaultSeamTransaction.java:123) [seam-persistence-3.0.1-SNAPSHOT.jar:]
at org.jboss.seam.transaction.DefaultSeamTransaction.isActive(DefaultSeamTransaction.java:52) [seam-persistence-3.0.1-SNAPSHOT.jar:]
at org.jboss.seam.persistence.ManagedPersistenceContextProxyHandler.closeAfterTransaction(ManagedPersistenceContextProxyHandler.java:130) [seam-persistence-3.0.1-SNAPSHOT.jar:]
at org.jboss.seam.persistence.ManagedPersistenceContextProxyHandler.invoke(ManagedPersistenceContextProxyHandler.java:91) [seam-persistence-3.0.1-SNAPSHOT.jar:]
at $Proxy325.closeAfterTransaction(Unknown Source) at org.jboss.seam.persistence.ManagedPersistenceContextBeanLifecycle.destroy(ManagedPersistenceContextBeanLifecycle.java:125) [seam-persistence-3.0.1-SNAPSHOT.jar:]
at org.jboss.seam.persistence.ManagedPersistenceContextBeanLifecycle.destroy(ManagedPersistenceContextBeanLifecycle.java:45) [seam-persistence-3.0.1-SNAPSHOT.jar:]
at org.jboss.seam.solder.bean.ImmutableBean.destroy(ImmutableBean.java:92) [seam-solder-3.0.0.Final.jar:]
at org.jboss.weld.context.ForwardingContextual.destroy(ForwardingContextual.java:34) [weld-core-1.1.2.AS7.jar:2011-07-06 12:26]
at org.jboss.weld.context.AbstractContext.destroy(AbstractContext.java:156) [weld-core-1.1.2.AS7.jar:2011-07-06 12:26]
at org.jboss.weld.context.AbstractContext.destroy(AbstractContext.java:173) [weld-core-1.1.2.AS7.jar:2011-07-06 12:26]
at org.jboss.weld.context.AbstractConversationContext.deactivate(AbstractConversationContext.java:218) [weld-core-1.1.2.AS7.jar:2011-07-06 12:26]
at org.jboss.weld.servlet.WeldListener.requestDestroyed(WeldListener.java:125) [weld-core-1.1.2.AS7.jar:2011-07-06 12:26]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:184) [jbossweb-7.0.0.CR4.jar:7.0.0.Final]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) [jbossweb-7.0.0.CR4.jar:7.0.0.Final]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) [jbossweb-7.0.0.CR4.jar:7.0.0.Final]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:362) [jbossweb-7.0.0.CR4.jar:7.0.0.Final]
at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:893) [jbossweb-7.0.0.CR4.jar:7.0.0.Final]
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:626) [jbossweb-7.0.0.CR4.jar:7.0.0.Final]
at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:2054) [jbossweb-7.0.0.CR4.jar:7.0.0.Final]
at java.lang.Thread.run(Thread.java:636) [:1.6.0_20]
Caused by: javax.naming.NamingException: Failed to get context with name comp
at org.jboss.as.naming.context.NamespaceObjectFactory.getObjectInstance(NamespaceObjectFactory.java:71)
at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:300) [:1.6.0_20]
at javax.naming.spi.NamingManager.getContext(NamingManager.java:439) [:1.6.0_20]
at javax.naming.spi.ContinuationContext.getTargetContext(ContinuationContext.java:55) [:1.6.0_20]
at javax.naming.spi.NamingManager.getContinuationContext(NamingManager.java:787) [:1.6.0_20]
at org.jboss.as.naming.NamingContext.lookup(NamingContext.java:175)
at org.jboss.as.naming.NamingContext.lookup(NamingContext.java:207)
at javax.naming.InitialContext.lookup(InitialContext.java:409) [:1.6.0_20]
at org.jboss.seam.transaction.DefaultSeamTransaction.getUserTransaction(DefaultSeamTransaction.java:142) [seam-persistence-3.0.1-SNAPSHOT.jar:]
at org.jboss.seam.transaction.DefaultSeamTransaction.createUTTransaction(DefaultSeamTransaction.java:136) [seam-persistence-3.0.1-SNAPSHOT.jar:]
at org.jboss.seam.transaction.DefaultSeamTransaction.getSeamTransaction(DefaultSeamTransaction.java:113) [seam-persistence-3.0.1-SNAPSHOT.jar:]
... 20 more