Just got a BBG from Seed Studio and it fails to boot the image from SD card. Following on the experience of the E14 BBB I hooked up a serial console and sure enough:
- Unable to read file /dtbs/am335x-bonegreen.dtb **
I confirmed that am335x-bonegreen.dtb on the board does not differ from am335x-boneblack.dtb on the SD card except in name so I copied the file with the "green" name and it boots and works normally. I will update the instructions.
The .dtb files should differ as the Green does not have HDMI. am335x-bonegreen.dtb should exist on newer images. It seems your problem could be related to the version of u-boot not aligning with the contents of the microSD card. Did you try holding the BOOT button when applying power to make sure the microSD card version of u-boot ran?