We recently ran into an issue where hundreds of documents had all of a sudden lost formatting. Bullet and numbered lists would appear simply as paragraphs with strange indents. The files were likely created in an older version of Office but we're not sure.
The files didn't look right in Word 2007 or Word 2003. However, when I opened the files in Word 2000 and OpenOffice, the files looked correct. Strange behavior. Re saving the files in OpenOffice seemed to have fixed the issue, however when some users would go to edit the documents further, the formatting would get lost again. We had to call PSS.
A case with Microsoft was opened and the following hot fixes were provided that solved our issue.