I just bought a 27RLS and it has the DV3200. I have been trying to get MP3 files to work with it. I have succeeded and thought I'd post what I did.
1. I'm using usb sticks of various size (8,16,32 gig)
2. Formatted as Fat32
3. Only 1 directory deep from the root directory.
4. Only 128 directories are allowed. If there are more they won't be seen.
if there are deeper levels of directories, the unit counts the number of files as normal, but when it tries to list the directory name and file information on the TV screen, it faults out and returns to the DVD not in slot screen.