If you're trying to report or investigate a bug, the best way to do it is to boil it down to an SSCCE
that demonstrates the problem in as few lines as possible. Every bug report contains one. Post it here and we can help you figure out what's going on, or we can point you to the official bug report site (where it may already have received a response).
Out of curiosity, have you tried it with more recent updates, or even Java 7? Java 6u18 seems pretty old. I just checked, and my system is at 6u26.