I got kernel-source-2.6.11 myself.
The kernel on the Knoppix CD is a custom kernel made with kernel-package.
When the 3.8 (Cebit 2005) version was released it was based on 2.6.11-rc3 (version from
www.kernel.org). I am pretty sure it has not changed for 3.8.1. If I use kernel-image-2.6.11
mu libusb problem goes away.