I haven't had a chance to hook up a USB interface and use a proper mic. But last night I broke out the laptop, muted the speakers based on what you said, recorded a few test recordings using the laptop's built-in mic (I know it would sound like gabage but was just seeing what would happen), but the audio was a jarbled (in and out, and kind of still echoing here and there as if the speakers were on). I'll give it a good test on a coming show when I get a chance.
If I come up with any other ideas that might possibly help, I'll be sure to share. :)