INVALID_CHARACTER_ERR: with autocomplete jquery plugin

Question

INVALID_CHARACTER_ERR: DOM Exception 5: An invalid or illegal character was specified, such as in an XML name.

I am getting this above error in my web inspector when I type anything in autocomplete text box. This error is specific to Safari ( with IE 7 as user agent ) and also on IE 7 / 8

$( '#fieldName' ).autocomplete( url, {
    width: 200,
    selectFirst: false,
    minChars:1,
    matchContains: true      
});

I am using jQuery 1.3