XML read error in AIR

Back to blogging, working on a couple of projects:

I was importing an XML file using the standard technique of using a URLLoader, and in the result handler, setting the XML file with:
var result:XML = new XML(event.target.data);

But I found I had to move this to the FileStream class in an AIR application because the user had to specify the XML file to load. So I used:
var result:XML = new XML(stream.readUTFBytes(stream.bytesAvailable));

Suddenly I was getting a 1088 error on this line:
TypeError: Error #1088: The markup in the document following the root element must be well-formed.

After checking and rechecking the XML, I found that for some reason, there was a byte at the beginning of the byteString, which was causing havoc with reading the XML. So the String being returned by the readUTFBytes method had to truncate the first character. Like so:
var fileData:String = stream.readUTFBytes(stream.bytesAvailable);
var result:XML = new XML(fileData.substr(1));