Interesting. Over the last three days or so, I've had 3 users, all on AT&T, complain about the same thing.
As of yesterday, my own BlackBerry (also on AT&T) is experiencing the same issue.
I only get data with WiFi. No EDGE or 3G, even though all indicators are good.
I suspect AT&T is having some data issues on their end that they haven't fully made public.
I'm hoping this one resolves itself soon, because I can already see how difficult it will be to explain to AT&T support what the problem is.