weird attempted escaping behaviour for javascript in post

Hi. Usually I have no problem posting javascript in my posts (actual javascript code that will run when displayed on a client as opposed to just displaying source code). But now I am having some difficulty getting the following to work in a post:

<script type="text/javascript">
function displayContent(json) { 

	var entries = json.feed.entry  || [];
	var closingPrices = [];
	var j = 0;
	for(i=41;i<=51;i++){
		closingPrices[j] = entries[i].content.$t.split(",")[0].split(":")[1].split(" ")[1];
		j++;
	}

	var image = "http://chart.apis.google.com/chart?chs=250x100&amp;cht=lc&amp;chxt=x,y,r"+
		"&amp;chxt=x,y,y&amp;chxl=0:|Nov%2028|Dec%205|12|1:|81|83|85|87|89|2:|in%2000s&amp;chds=81,89";
	var chd = "&amp;chd=t:"
	for(i=0;i<closingPrices.length;i++){
		if(i>0) chd = chd + ",";
		chd = chd + (""+(closingPrices[i]/100));
	}
	image = image + chd;

	document.getElementById("chart").src = image;

}
</script>

For some reason, wordpress encodes some of the double quotes before uploading (“) but not others. Thus when I view the page the javascript fails with syntax errors on these wrongly encoded double quotes.

The quotes that are changed to “ in the above code are emboldened as follows:
if(i>0) chd = chd + “,“;
chd = chd + (““+(closingPrices[i]/100));
…
document.getElementById(“chart“).src = image;

Why would WordPress encode some but not all and how can I prevent it from doing so?