Ah, this is frustrating! I just noticed it does the same thing for me. Any fixes?
You are the first person to reply to me ever and my post has been up for nearly 6 months. I have tried asking Adobe for help but they have no clue what I am talking about and I have even tried asking Viewcast for help. Viewcast says that Microsoft changed something when they went to Vista which is causing this issue.
I want to use Win 7 to take advantage of more than 4GB of ram but it has a serious flaw with the audio. I haven't checked to see if there are any new drivers for the Osprety card that could possibly fix this however.
I am currently correcting this by using a converter before the encoder to mono the two channels together and I just leave Adobe in stereo. I just happen to have gear laying around to do this but something like what I am using is really expensive.
Sorry I can't be more help but I myself am stuck.