[syslinux] Unable to boot my USB flash drive, even with USB-ZIP trick...

[Nazo]

I've been using a USB flash drive for quite a while now, and in my
previous system it worked great, but, I find with my new motherboard
now that I have upgraded I can't boot it.  So I decided to try the
trick mentioned in the README.usbkey file where you make a ZIP drive
like image on the flash drive and set the BIOS to boot a USB ZIP drive
instead.  Unfortunately, it still doesn't work.  It never even says
Booting USB-ZIP or something (when it's booting a CD-ROM, it says
"Booting CDROM" while it loads.)  Probably the most curious thing
about this situation though, is the fact that the BIOS explicitely
SAYS that it has found a USB storage device!  In the information it
shows on the top of the screen just after the initial POST testing and
just before it starts to actually boot, I see text informing me that
it has recognized my USB storage device.  It does not show ANY
information on any other USB devices such as my printer, which say to
me that it's not simply informing me of all USB devices it sees, but,
specifically pointing out that it actually recognizes that particular
device for what it is.

In case it's related, this is the mkdiskimage command line I used to
the best of my memory:
mkdiskimage -4 /dev/sda 239 64 32

I used 239 cylinders even though I have a 256MB device just in the
hopes that maybe it will increase compatibility on some weirder
systems out there by some maybe 1%, but, it probably does nothing. 
Still, I'm strapped for space, but, I can still afford to give up <6MB
just in that vague possibility it will be more likely that more
systems will accept the drive.  I keep diagnostic tools and such on
this flash drive to help me diagnose and fix problems -- which is part
of why I need to get it bootable again...