Hello.
I am so glad to say your links are wrong. The first and the second go to the overview page, in fact any wrong link goes to overview, try:
http://www.fusioncharts.com/widgets/docs/?Contents/noValidInfo
The last one is a link to the old documentation, recent versions of amcharts do not use setDataXML(strXML). You changed it to setXMLUrl(strXML). If I use old method no request is done and it paints no gauge. At least with the new command it shows the gauge the first time...
Regards.