Help with Flash CS4 and AS3

I am trying to create an audio that only uses the first entry in an xml file. I have most of the things working but I keep getting an error related to the audio file.

TypeError: Error #1034: Type Coercion failed: cannot convert “” to
at latestMessage_fla::MainTimeline/frame1()

I inserted the url for the file into error message so you can see if there is s problem with that. I was initially trying to use a variable to hold the url for me, because this xml file gets updated every week and I only want to access the most recent entry.

This is my first attempt at making an audio player in flash, so I am sure I have made a simple mistake, but for the life of me I cannot figure out what it is.

One last question is in regards to using id3 tags versus xml tags to fill dynamic text fields in the player. Currently I am using the xml file to do this, are there any advantages one way or the other for this. The only reason I ask is that I am hoping to display an “album art” image from the id3 tag in the player. Would it be better to grab all of the information from the mp3 file?