Its a known issue right now for us using romer and the D2G... seems like Liberty installs some sort of "update" when your phone reboots no more 3G or data at all. Check out this thread to get 2.0 which is working for some but I even had issues with 2.0 and data and just went back to 1.5. Couple of people are trying to see what's causing it
Hey I found that a temporary fix--especially if you don't reboot often--is to simple go back into Clockwork and reflash liberty 2.0.1 and the rommer....then you have 3g again. At least you don't have to deal with the time of creating a backup.