Seam jee5 booking example at http://anonsvn.jboss.org/repos/seam/branches/community/Seam_2_2/examples/jee5/booking can't get connection from java:/DefaultDS due to wrong setup of CONNECTION_PROVIDER in org.hibernate.ejb.Ejb3Configuration. This is caused by jtaDataSource = null in org.jboss.jpa.impl.deployment.PersistenceUnitInfoImpl.jtaDataSource.

From quick debugging - PersistentUnitMetaData has got these properties:
PersistenceUnitMetaData@c6d08c4{provider=org.hibernate.ejb.HibernatePersistence, jta-data-source=java:/DefaultDS, non-jta-data-source=null, non-jta-data-source=null, excludeUnlistedClasses=false, properties=

{hibernate.cache.provider_class=org.hibernate.cache.HashtableCacheProvider, hibernate.hbm2ddl.auto=create-drop, hibernate.transaction.flush_before_completion=true, hibernate.show_sql=true, hibernate.dialect=org.hibernate.dialect.HSQLDialect}

, name=bookingDatabase, transactionType=null}

but when jtaDataSource should be set, it is not found in a context and it is set null value to org.jboss.jpa.impl.deployment.PersistenceUnitInfoImpl.jtaDataSource :

if (metaData.getJtaDataSource() != null)

{ this.setJtaDataSource((javax.sql.DataSource) ctx.lookup(metaData.getJtaDataSource())); }