I need to bump this thread, since I have exactly the same problem. It's probably some loop somewhere or line-in just not working. I have to say that I'm trying this on an MCE XP so maybe it's some other app controlling the SC. I sure can't get responce from the mic via line-in, but it seems to get the generated signal from somewhere. I'm using the onboard AC97 on an Asus A8N32-SLI motherboard
This is what the chart looks like
test.GIF