If you have the option "On doubleclick or enter in the
library" set to "Enqueue the selected item(s)" rather
than "Play the selected items(s)" then ml_www will
clear the playlist and begin playing the selected song
when you use the include links in your browser.
This is because ml_www uses a wierd method to enqueue
the requested file. It asks the medialibrary to send
the command to winamp rather than doing it itself...