If you have a MS VX 1000 Webcam running under Linux/Debian you may experience 'no sound'.
The problem is down to the way the driver assigns bandwidth to the video, which ultimately hogs all that's available and sound gets none.
I read the developers have a patch thats been applied and included in all drivers included in kernel from 2.6.38 onwards.
If you are running a kernel version older than 2.6.36, upgrade your kernel.
This should fix your sound problems.