I'm not using the G45, but without trawling through all the AT91Bootstrap and U-Boot source trees for the G45, I can suggest you get to the U-Boot console, and get it to print out the environment settings. It should be clear from U-Boot whether it is using NAND flash, or data flash, and the addresses being used.
In SAM-BA its a matter of picking the NAND or data flash tab, initializing the memory, and downloading at file to the address required. Those addresses for AT91BootStrap, U-Boot, U-boot environment, uImage, and file system images should be relatively easy to confirm in the source (open as it is) for the components, and the environment for U-Boot (or it's defaults) and the parameters passed to the kernel.
http://www.at91.com/linux4sam/bin/view/ ... emo_Memory