Some KML files generated by Xastir 1.9.9 will not open in Google Earth. Upon further investigation, an ampersand (&) character in a Placename was causing this. Removing the offending character fixed the issue.
Sample file attached. Offending character is on line 5980.
KML uses xml, so we'll need to convert to html entities or wrap in CDATA. There is a brief discussion of html in feature names in the KML documentation at: https://developers.google.com/kml/documentation/kmlreference#feature
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