I finally got around to updating my BIOS using the @BIOS tool Vitalis described from the Gigabyte website (thanks Vitalis!), and so far it's working GREAT! Everything syncs as it should, and I've had no error messages. I've said this before, but I have a feeling this is the problem. Thanks again to everyone. The collaboative problem-solving comminuty of this discussion thread ALMOST makes me feel better about the HOURS I've lost on this.
I'm wondering, do you all think this is a Gigabyte problem, or an Apple problem? Either way, SOMEONE ought to solve it. It was ALMOST enough for me to go out and get a droid.
Also, FYI, I tried the DFU mode thing, and it didn't help at all.