Blaine Tuisee 0 Newbie Poster

I have been running this application for some time and have just recently begun to receive this error message. I would be eternally grateful if someone could shed some light on what causes this error or it's possible sideffects.

04/27/2010 00:06:16.016 [ERROR] com.ghd.domain.GHSessionFactory.createSession(GHSessionFactory.java:129) - An open thread session is being replaced. This will cause connection leaks and needs immediate attention!
java.lang.Exception