This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
It looks like you are trying to use a DOM feature which hasn't been implemented in Xerces, which from the stack trace looks like the HTML module. Try the following program to check what modules your implementation supports.
subject: Anyone understand what this exception means