This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
You are using the no argument constructor of BeanComparator. Have you executed the setProperty() method? If you do not then BeanComparator will try to compare the two objects the "usual way". Alternatively, you can use one of the other two BeanComparator constructors.