When performance of Firmware update, it can be pretty common for the Firmware to reset the unt back to "out of the box" default settings. Have you tried going into the setup menu to see if the audio output settings are the same?
I upgrade my BDP1600 to the latest firmware yesterday. The upgrade went smoothly and the player power off by itself after completion. Last night when I try to play a DVD there was no audio. I tried another DVD with same result. Streaming from Netflix also has no audio.
Anyone has same issue after upgrade or know how to get audio back?