I’m not familiar with OC4J or domino, but…
purge_calls() is calling Thread.stop(). That’s really bad. The stopped thread could be sitting on locks. Sun deprecated it and disparaged the method, starting in like 1996. It’s not safe at all. (Have a look at the JDK5 javadocs for this little gremlin.)
You might double-check that you’ve got an up-to-date orb. If you do, send the crew at lotus a bug report.
Hope that helps,