Are you referring to a single Quick Style or an entire Quick Style Set? If
the latter then the existing document needs to be formatted with the same
styles (names) as those in the Quick Style Set. So if the document contains
manual formatting only, or uses styles that aren't found in the Quick Style
Set, then when you select a new Quick Style Set you won't see any changes
made to the document. If that's the case then you need to format the
document using the styles in the Quick Style Set.

Please post all follow-up questions to the newsgroup. Requests for
assistance by email cannot be acknowledged.

~~~~~~~~~~~~~~~
Beth Melton
Microsoft Office MVP

Coauthor of Word 2007 Inside Out:
http://www.microsoft.com/MSPress/books/9801.aspx#AboutTheBook