On Sunday's ride my powertap stopped producing power readouts (mated to a Garmin 705). I assumed it was batteries, even though there was no low battery warning. Changed them on Tuesday but it's still not producing any readouts. I know this has happened before as there are some stories on t'interweb, but the story never seems to get seen through to conclusion. Has anyone any idea what the problem might be? I feel blind training without power!