The jodconverter plugin needs to be upgraded to support OpenOffice 3.3. Please see the following issue in the jodconverter issue tracker for a specific OpenOffice 3.3 issue and resolution:
According to a note in the xwiki-platform-office-importer/pom.xml, the currently used jodconverter plugin is a custom xwiki build. Can a new custom build be generated from the jodconverter trunk? I have built my own local copy of the jodconverter trunk successfully, but I am unsure how to deploy it into my existing xwiki instance. If you can give me any pointers on where to start, I can attempt to build/test on my own and document.