I have just bought this player and there is very low sound coming from the centre channel - it has the latest firmware and I have tested the HDMI cable but wheb I have it set to PCM output I am getting very low centre channel sound.
My first guess would be that you have a channel level calibration problem and need to recalibrate your surround system. My second guess would be to take a look at what format your processor/receiver is applying to the input. Perhaps you need to select a different one.