Are you sure you set the right Code Page (character set) for encoding in the Page/Web.config?
I use encoding ="1252" instead of UTF-8, as I need to show some data coded for German and Latinamerican language.
Remember to use always the same encoding, as an special character (outside de 255 normal characters), may be represented differently with a different encoding.
PS: See more info on Code Page in: http://msdn.microsoft.com/en-us/library/dd317756(v=vs.85).aspx
Diego Barnech, May 11, 2011