It sounds like your XML has the ´ ACUTE ACCENT
character encoded in ISO-8859-1 as 0xB4, even though it should be 0xC2 0xB4 in UTF-8. This usually happens when people produce XML by concatenating strings instead of using a proper XML library that is aware of encoding.
Is my assumption correct? Then you have to fix the problem with preprocessing in order to make an standard compliant XML stream. Either replace the byte as above, or if it really affects all bytes in the range 0x80 to 0xFF, simply change the encoding declaration in the XML prolog, e.g.:
<?xml version="1.0" encoding="ISO-8859-1" ?>