Maybe Gene can, in his April '07 review he reports that it works: "As an added bonus, you could even store some music files on a USB flash drive or portable hard drive and connect it right to the front panel USB connector for instant access to your music."
In Yamaha's description of the USB port, they only talk about flash drives & portable music players, not large external hard drives.
Why not talk it over with your vendor, or Yamaha tech support?