Got a bug report....
In Kismet, if the AP is running with broadcast SSID turned off, and if it doesn't discover the SSID through association response, the logged ssid is "<no ssid>". When processed through the script, the kml file contains the line:
GoogleEarth returns an error on this line, specifically:
Parse Error: expected equal sign at line: ##
Obviously it's the <> around the "no ssid".
I'm not a PHP expert, but I'll beat on it a bit.