>burn it in a Dual-Layer DVD
I don't know how this relates to a Mac, but this is what has to be done for dual layer on the Windows side of things
Run as Administrator http://forums.adobe.com/thread/969395 (Encore AND PPro)
Also, go back to http://forums.adobe.com/community/encore and enter
in the line under ASK A QUESTION to see previous discussions... be sure to click the See More Results at the bottom of the initial, short list if the initial list does not answer your question
I transcode them in advance ("Transcode now").
I've already deleted the timelines AND assets and re-create them and re-transcoded them and still the same problem.
About the excess tracks, after the transcode the audio track for some reason ends up being a little bit longer than the video track.
Previous times, I trim that out and the problem is fixed but not this time.