Any idea why the webcam interferes with the scanner?
@mjbjr - I bet I know what it is, I've experienced a similar issue. When you plug in the usb webcam, it adds another audio device and this becomes the default audio input device for the computer. So if you plug in the webcam, and then go Start->Control Panel->Sound and Audio Devices Properties and click on the Audio or Voice tabs (assuming Windows XP), I'm guessing Default Device will show up as something like USB Audio Codec or some such. You can select your normal sound card from the drop down list and everything should go back to working the way it was. Be forewarned though, next time you plug the webcam back in, it will go right back to the same thing.
So in other words, you were listening to the webcam's mic in whatever room you have your comptuer in over the stream.