Sorry, the camcorder is a Canon Vixia HF G10. I should also mention I use a second camera, a Canon HV-20, and use the multi-camera features of CS6 (and CS5 before that) to create a two-camera sequence. While I can understand that the camcorder model numbers may be important, I'll reiterate that I've used these same camcorders for many projects before this and have never experienced this "conversion" problem before.
I'll also admit that I've never used this method of creating a sequence before, and I've probably been doing it "wrong" all along. I generally create a new sequence, pick something close from the list (e.g., HDV 1080i30), then drag my video into the sequence, and when asked by Premiere Pro if it should alter the sequence settings to match the footage, I click Yes. This is the way I've always done it before, and it's always worked flawlessly.
I suppose that perhaps I inadvertantly didn't click Yes once this time around. Though if that were the case, I would have figured I'd end up with problems when trying to nest my sequences for purposes of multicamera work. Also, I can't imagine how I was able to successfully convert my final sequence into a perfectly fine blu-ray image.
In any event, I tried taking my short version of the finished sequnece and exporting it to an MP4 using the H.264 format and the HD 1080i 29.97 preset. Then I imported the MP4 and created a sequence from the MP4 using the right-click, Create Sequence From Clip method. Then I exported that sequence to a widescreen AVI and it worked; I saw both video and audio.
So I guess I'll try using this procedure with my completed 90 minute sequence overnight tonight, and I'll let you know if it works. Thanks for the tip!