First thing: are you trying to use the ArcGIS API for JavaScript or the ArcGIS JavaScript Extension for the Google Maps API? Your html references the former, but your code looks like it's written for the latter. Also, you should pick one of the following, not both to run LoadMap:dojo.addOnLoad(LoadMap)
<body class="tundra" onload="LoadMap();" onunload="GUnload();">
Finally, and this is probably the cause of the error you're posting, change this:content:"<div style='width:275px; height:175px;'><b>Total 2007 Census Block Population is " + att.S2001 + ".</b><br />The age breakdown is as follows. <br />"
+ "<img height=100 width=250 src='http://chart.apis.google.com/chart?cht=bvs&chs=250x100&chd=t:"
+ S2001 "," + S2002 + "," + S2003 + "," + S2004 + "&/></div>"};
To this:content:"<div style='width:275px; height:175px;'><b>Total 2007 Census Block Population is " + att.S2001 + ".</b><br />The age breakdown is as follows. <br />" +
"<img height=100 width=250 src='http://chart.apis.google.com/chart?cht=bvs&chs=250x100&chd=t:" +
S2001 "," + S2002 + "," + S2003 + "," + S2004 + "&/></div>"};
Notice the + at the end of the line rather than at the beginning of a new line.