USB booting :: boot: cannot find image

ok , Finally, I found the solution.

The problem was the fact that my key was detected as /dev/sda. (and not /dev/sda1)

I've done in root:
# cfdisk /dev/sda
I create a full primary partition on it in FAT 16 (code 06 in my cfdisk)
I wrote and quit

I download syslinux 2.13
then I wrote:

# dd if=mbr.bin of=/dev/sda
(for a nice mbr on the usb stick) and:

# ./syslinux /dev/sda1

and it works fine!
thanks for your help.

original here.