I found after rooting my Ermine, that I hit an infinite loop after a couple cycles of powering. The only way I got it back was to down-flash it with the USB stick. I made sure the USB stick was clean, formatted to default block sizes, etc. Then copied over only the update.zip to the root of the stick itself. Booted, flashed, and was back in business.

If the USB stick is giving you problems in flashing back to Dingo, then it could be that the bootloader doesn't recognize the format of the USB stick, like I mentioned above, make sure it's cleaned off, and formatted right, then copy only the update.zip over. Holding the rotate and menu buttons are essential as this notifies the bootloader that you want to flash, and not boot off the eeprom.