I got a BDP 5200 with Software 1.55 and i tried some tests for surround sound. The problem is that the audio files i found in the Microsoft site and everywhere else are not supported by the BD Player, even when they are WMA (which is supported by the player).

Anyone knows of a tested file that works for this 5200 model? By the way the ones that didn't work were 2 files, one for 5.1 and the other for 7.1