Yes, this is exactly what I would like to try - create two standalone jbosses and loadbalance them using Apache, so the visitors traffic is divided between two of them.
Regarding your issues, I think it's same as mine:
Thread: ajp-0.0.0.0-8009-813 : priority:5, demon:true, threadId:1431, threadState:RUNNABLE
org.jboss.naming.ENCFactory.getObjectInstance(ENCFactory.java:114)
- locked <0x7406ce55> (a java.util.WeakHashMap)
javax.naming.spi.NamingManager.getObjectInstance(Unknown Source)
javax.naming.spi.NamingManager.getContext(Unknown Source)
javax.naming.spi.ContinuationContext.getTargetContext(Unknown Source)
javax.naming.spi.NamingManager.getContinuationContext(Unknown Source)
org.jnp.interfaces.NamingContext.lookup(NamingContext.java:832)
org.jnp.interfaces.NamingContext.lookup(NamingContext.java:686)
javax.naming.InitialContext.lookup(Unknown Source)
org.jboss.seam.transaction.Transaction.getUserTransaction(Transaction.java:82)
and other threads waiting for weakhashmap. BTW, I am using JBoss 5.1 standalone, not EAP.