Samsung Moment :: Repeated Loss Of Data Connection

I keep having this problem with my Moment where it will refuse to do data connections. Sometimes rebooting helps, sometimes it doesn't. It happened three times today, and I was ready to throw my phone out the car window. It's happened on and off since I got the phone 2 months ago. I hoped it would go away after I updated to 2.1, but no dice. My wife, who doesn't use the phone as heavily, doesn't have these problems. Some days (like today) it seems worse than others. I see scattered forum posts about "evdo lockup" and "cdma lockup", but no real idea of how to diagnose what the problem is, and more importantly, whether it's worth taking it back to Sprint and trying to get them to do somethin.