You may have found a fix for this old issue by now, but I recently bought a dv9700 and had the same problem. Turns out there is a conflict between the uvcvideo (webcam) kernel module and the usb-storage module. If uvcvideo is blacklisted in /etc/modules.d/blacklist then usb automount functions as it should (and the webcam will not work of course).

I also have a dv6500 but both drivers happily coexist. Obviously different systems. Strange.

Thought this may help ...