If you're using both Office 2007 and 2010 (for example on two different computers) for editing the same document and you have some automatic fields inside document edited in Word, you may find that they're not properly updated.
This is especially important if you're using auto-fields with numeric references to the pages or referencing other parts of texts via headings. For example - automatic table of contents or bookmarks containing heading's title, page number or level. After you open and save in Word 2010 document previously edited in Word 2007 and then reopen it again in Office Word, you may find these fields not updated or incorrectly updated. Not updated - meaning, that they reference wrong item or page number. Incorrectly updated - that table of contets contains proper entries (based on headings) but all with page number set to the same as first page of table of contents (i.e. referencing itself).
Full document refresh (Ctrl+A for selecting all the text plus F9 for updating all fields in selection) should do the trick. But you have to remember about this, especially before printing the doc or making PDF out of it.