USB-ZIP boot problem

I have been using the makeusb.sh script with makebootfat to program a usb
key. I am using an Advantech SOM-2353 board, an AMD Geode based board. The
utility works fine and programs the stick. When I use small stick (32Mb)
syslinux boots fine and loads the kernel. When I use a large stick (1GB)
says: "cannot find kernel image". Both sticks boot fine on my dell laptop.
On the board USB-ZIP is the only boot option that works, USB-HDD and USB-FDD
completely ignore the USB. Any assistance would be appreciated. 

 

Does anyone know where I can get information on the workings of USB-ZIP and
bootability.