I found this at www.pioneerelectronics.com:
" Presenting a 6-disc changer unlike any other: the XDV-P90. In addition to playing standard audio CD/CD-Rs, it can handle DVD Video and Video CDs. "
It does not state DVD audio in that statement.
I also found this at www.ulead.com:
" Got a new Audio-DVD player in your home or car? Ulead Burn.Now software will let you put hundreds of CD-quality songs on one Audio-DVD disc. "
Is it a possiblity you are not configuring your "burning" software to achieve the proper playback methods?
Hope any of this helps.