For some reason, talking heads don't run in sync with their audio in Camtasia output. Some videos get a worse case than others. It ranges from "noticeable" to "annoying".
Solution: write the audio to an mp3, then pull it back in as track 2. Use the pip audio to get your new audio roughly lined up, then kill the pip audio. Now, by trial and error, adjust the sound back on the track so that it is even or slightly behind the video.
Think about it: because light travels faster than sound, we humans are accustomed to seeing someone talk before we hear their voice. The further away they are, the greater the differences. So if the video is slightly ahead of the audio, I'm guessing that most people wouldn't even pick up on it.
But having the sound arrive first is something we never experience in real life, so use this trick to avoid it in your videos.
Are there advantages to using FLV video over swf - apart from image quality ?
FLV is much more tolerant of high-motion and length, yet it takes a lot longer to encode.