In case it helps I've just run epubcheck.jar 'raw' from a Windows CMD box. This was the output:
Code:
java -jar epubcheck.jar broken.epub
Validating using EPUB version 2.0.1 rules.
FATAL(RSC-016): broken.epub/OEBPS/Text/Section0001.xhtml(10,29): Fatal Error while parsing file 'The element type "b" must be terminated by the matching end-tag "</b>".'.
ERROR(RSC-005): broken.epub/OEBPS/Text/Section0001.xhtml(-1,-1): Error while parsing file 'The element type "b" must be terminated by the matching end-tag "</b>".'.
Check finished with errors
epubcheck completed