Success!  I have now printed a few parts from the SD card!  This is one of the nice features of the MakerBot electronics– you can print from a file that lives on an SD card plugged directly into the MakerBot. You load the file, insert the card, initiate the print from your USB-tethered computer… then once it starts printing, you can unplug the computer and it will print untethered. The main benefit is that it frees up your computer. It makes a lot of sense if you are setting up to print multiple parts in a row – an advantage of the automated build platform.