I should have mentioned that I already tried both Upgrade and Upgrade and Erase on the download page. Those are the only buttons that aren't greyed out and inactive.
When I try both, the application times out while waiting to recognize the board.
The LED's on the Revo do their usual blink sequence when the USB cable is plugged in, so it must be getting power.
Is there a way to restore the board to it's factory default configuration that doesn't necessitate a connection to the GCS?