I have experienced such a problem too, with live-cds most of time. It says "Stopping usb hotplugging" and then hangs for hours...
What about manually (un)loading you usb modules ?
You could also build them in the kernel and go with udev... That's what I'm doing and the device nodes are automagically created and deleted...
Perhaps you could also tweak usb.agent or something like that ?
]]>