We have a problem with xinha, compile_update_string() and query_parameters(). Xinha changes double quotes, ampersands, the less than symbol, the greater than symbol and probably others into their HTML Ampersand Character Codes[1]. This conflicts with what mysql_real_escape_string() does and causes query_parameters() to refuse to update the database when there is an one of these characters in a Xinha field.
I have investigated this for quite a while now and am unsatisfied with any quick solution that have looked at.
[1] http://rabbit.eng.miami.edu/info/htmlchars.html
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Tony Lambregts