-boot -hda //.//physicaldrivex does not work if it is USB drive

qemu-system-x86_64.exe -L . -name "RMPrepUSB Emulation Session" -boot c -m 500 -hda //./PhysicalDrive1

just opens a blank QEMU window (no BIOS POSt messages) and does nothing

qemu v 0.15.0
Under Windows 7 64-bit
drive1 is a USB Flash drive

Previous version of x86_64 (Jan 2010) works fine. If replace with new version (or RC2 version) then does not work.

if use harddisk.img raw file instead of USB physical device then I get BIOS POST messages and it boots to image OK.
So appears to be USB or physicaldisk support issue???