Trouble booting from USB flash

[ball%grex.org@localhost (Andy Ball)]

Hello,

    I just tried booting a VIA EPIA M10000 mITX board (1 GHz
VIA C3 single-core microprocessor) from a USB flash drive
that I'd written NetBSD-6.1.4-i386-install.img to.  It says
"NetBSD/x86 ffsv1 bootloader", the cursor moves down a
couple of lines and then nothing.  The USB ports on this
board are probably quite slow but the activity light on the
USB flash drive is not lit or flashing.  I would welcome any
suggestions.

Thanks,
  -Andy Ball