Ever since first doing this hack I've had a real problem with keeping the thing powered. USB power seems to die if you look at the thing wrong.

At first I thought I was browning-out the incoming power but adding a capacitor didn't fix it. I resoldered the power connections, and even clipped off the pin connectors to make direct solder joints. No dice. If you shake it around the power blinks on and off.

I think I finally tracked it down to a shoddy power cable that came with the clock. It's USB on one side and barrel jack on the other. I don't have the same size barrel connector on hand so I just unscrewed the port inside the clock and soldered a new USB cable in its place. So far so good.