There's a number of critical steps that aren't always highlighted as well as they should be in every tutorial.

The device doesn't actually shut down when it's on the charger, it simply goes into what basically amounts to a lower run level, X is still up (to show the charging info), so it's booted past the point where you can start the flashing process.

Anyway, to anybody who discovers this thread in the future, a few points:

1. The charger must be unplugged so the device can shut down completely. You're welcome to plug it in once the device is waiting for the flasher (USB image in the upper right corner after powering up with Home/Swap key held down), or in the process of flashing.
2. In order to get the device to wait for the flasher, most every guide mentions that you must boot holding down the Home/Swap keys, but what they don't mention is that you also need to have the USB cable plugged in when you do this.

There are a disturbing number of tablet users in Florida, especially the bay area. . . .