I am editing a multi-cam sequence, and all of a sudden for some reason it is only playing back the left channel of audio. The nested clip that holds all of the source tracks plays just fine, and the source clips themselves play fine (I can use Match Frame to find a given frame in the original, and it plays in stereo in the source window), both channels of audio are there in each case. But when I play back the video from the main program window, I hear only the left channel of audio, no matter which camera's clip is being played.

System:

Mac Pro dual 6-core 2.66GHz Xeon with NVidia GTX285, 16GB RAM

OS X 10.7.3 (11D50)

Premiere CS 5.5.2 (all updates applied as of today)

I've looked at the mixer, everything is panned center, and the signal is only showing up in the left channel. All of my audio for the multi-cam mix is on a single audio track, but that has never kept my audio from being in stereo before. There are no effects on the track, and I can't find any other modification to the multi-cam mix that would affect the audio by rendering it on only one channel.

The source audio is coming straight from my MTS video files, hasn't caused any issues so far. I combined a batch of footage and their associated audio file into a sequence, used Pluraleyes to sync everything up, took my new, synced sequence, nested it, and enabled multicam editing. I've been working with it for a couple of days and only today did it suddenly start giving me only one track of audio, and it happens in the new multicam sequence.

I've tried pasting the original audio into the multicam sequence, but I've made enough cuts that it would be a massive effort to sync everything. I've tried duplicating the one audio track that I have (the one the plays only the left channel) and pasting it into another track to see if I could do a "mono to stereo" fake, but when I do that and try to preview it, I get a "Rendering Required Files..." dialog box that never progresses and never goes away unless I cancel - no preview.

So... any thoughts, anyone? I am not a Premiere guru, but I am having some trouble figuring out why this is happening.

Thanks in advance,

Matt