I have noticed something wrong in the javadocs commnets for JtaTransactionManager.
I was trying to do a PROPAGATION_REQUIRES_NEW transaction with a JTA transaction manager on Resin 3.0.13. As the documentation says, the location for the transaction manager should be: "java:comp/UserTransaction". But for Resin 3. 0.13 actually it seems to be: "java:/TransactionManager".
I did not checked with an older version of Resin, maybe it has changed in the meanwhile.