I have to say that I've had many times where the data connection will just stop working. You can see the up arrow blinking like it's sending data, but never receives any back. I toggle the 2G only option in the settings menu to make it reset the data connection, and it usually starts working again. I've noticed the phone itself drop the data connection (Edge/3G icon goes away and comes back a few seconds later) if it stops working for long enough. I'd just go ahead and reboot the phone, see what happens.