Thank you for your prompt reply Toshiya. When testing with SOA 5 on 6/1 I received numerous "JbpmException: cannot mark externally managed transaction for rollback" messages in my log file. I hadn't enabled all of my logging at this point, but since I'd seen this same message with my JBoss AS 5.1.0GA/JBoss ESB 4.7/JBPM 3.2.5 configuration, I thought that SOA-5 had the same problem. After receiving your response this morning, I enabled all of my logging and reran my test on SOA 5 with a jms-jca provider and a BPMProcessor call. It worked!! I don't know why my 6/1 testing had such different results, but without the more detailed logging, any conclusions would be guesses.
Thanks again,
Jennifer