Thumbnail paths in XSPF Playlist are relative, causing no thumbnail to display when URL has 'subfolders'

I have a sample node's playlist shown below. The location field shows an absolute path, so the videos display perfectly with FLV Media player on my node. But as you can see, the images seem to have a relative path. So if my node is http://www.mydomain.com/mycategory/video-node, it's looking for "mycategory/files/myimage.jpg" instead of "files/myimage.jpg"

- <playlist version="1" xmlns="http://xspf.org/ns/0/">
  <title>Test Video Node</title> 
  <info /> 
  <link>http://www.mydomain.com/</link> 
  <annotation /> 
- <trackList>
  <track /> 
- <track>
  <creator>admin</creator> 
  <image>files/myimage.jpg</image> 
  <location>http://www.mydomain.com/files/welcome.flv</location> 
  <info>http://www.mydomain.com/node/87</info> 
  <type rel="flv">flv</type> 
  <title>Video One Title</title> 
  <identifier>87</identifier> 
  </track>
  </trackList>
  </playlist>