It's dead, Jim...
So after 6+ years of faithful service, my TiBook died just now, with a buzzing sound (not hard drive, somewhere in the upper right-hand corner of the logic board under the keyboard).
I'll have to search around to see if this is something recoverable or not. I didn't have any important data on it, but he was the box that powered my third screen, as described previously.
Must... Resist... Buy... New... Mac...