I have also had a similar experience with my Storm 2 on OS .607 based hybrid. Each time it occurred in the early morning 5 am or so. The phone would show 3G but if you opened an app that needs data I get a no data connection window. Go to manage connections short cut on my theme and turn the mobile connection OFF then ON and it works fine.
This happened a few weeks ago, once or twice then again the following week but I can't say that I've seen it again in the last week or so. It has only occurred at home.