I have a Toshiba SD-34VESE DVD player, same problem : no access to any menu to choose the audio format. It selects automatically the DVD-A layer, which leads to a poor 2-ch sound.
Now what I did to go around the problem : I copied the DVD-V files (VOB type) on my PC, and then tried to read it through a showcenter 200 linked to my PC via ethernet, and then via optical to my amplifier.
There are 3 VOB files : 2 of 1Go and one of 600 Mo. The small ones provides a very good 5.1 DTS sound ! However, only the end of the record is given (From Back in the USSR). With the 2 big VOB files, no way, still poor 2 ch sound. Another strange thing is that the date of the small file has been changed to the current date, as the one of the big ones was unchanged.
All this very interesting but I cannot explain yet.
Anyone with a brillant idea ???