MS OOXML

Foisted on their on petard.

http://www.theregister.co.uk/2008/04/22/
office_2007_oxml_fails_test/

Microsoft's Office 2007 Word documents do not conform to the newly-approved Open XML (OXML) international standard.

Alex Brown, who heads up the group responsible for maintaining the OXML standard at the International Standardisation Organisation (ISO), revealed the less-than-pretty findings in a blog post late last week.
.....
Microsoft had tried to fast-track OOXML via Ecma International, the group which originally rubber-stamped the format. However, a vote of the draft failed to gain sufficient approval last September.

The Ecma-approved version of OOXML conformed to Office 2007 documents, but, following the changes made at the BRM, the wheels appear to have fallen off.

Oh yeah.