I've had my Moment for a week now and I've had this happen 3-4 times already. My guess is it has to be a bug that will most likely get fixed when 2.1 is released. It's happened consistently when I have not turned my phone on since leaving one cell site area and gone into another. I drive 3 miles to a park and ride to go to work and twice this week the data has crapped out. Could see the EVDO data upload activity but nothing worked. I tried to 'reset' it by trying to go into Airplane mode but this would cause it to freeze. After trying to get into airplane mode, the data icon would disappear but the cel signal bar would show no bars and no "x" or "Airplane". Trying to get out of airplane mode was fruitless (it was greyed out) so I had to pull the battery. Of note, while it showed 'no bars' and was in airplane mode limbo, I called my home phone (a Vonage line) to see if it would ring. No ring, only silence, but when I checked later, I had a message from my cel that was pure silence. I checked my usage on Sprint and it hadn't changed (no anytime minutes used). I can live with powering on/off in the morning until a fix is found.