I am using jboss3.2.5. In conf we have jboss-service.xml file which has some transaction settings. You may want to try tweaking it.
<mbean code="org.jboss.tm.TransactionManagerService"
name="jboss:service=TransactionManager"
xmbean-dd="resource:xmdesc/TransactionManagerService-xmbean.xml">
<attribute name="TransactionTimeout">300</attribute>
<depends optional-attribute-name="XidFactory">jboss:service=XidFactory</depends>
</mbean>
I have not tried jboss 3.2.4.
Good Luck :-)