I have discovered an issue when using iReport in combination with XML File Datasources.
Every time I open iReport and start the development of a new document it will result in a XALAN error when trying to preview the document. java.lang.NoClassDefFoundError: org/apache/xpath/CachedXPathAPI
Once I for example switch back to 'XML' view and back to design I'm able to preview the result. Once I was able to preview the result I'm able to design new reports without any error.
In addition the issue only occurs when creating a new XML datasource report after starting iReport. Opening a XML report with iReport works directly. It's only when you start to create after opening iReport that the issue occurs.