Tried reseting connection?
Toggling Airplane mode on-off?
Try selecting a network operator? setting --> wireless & network --> mobile network --> network operator?
Oh and check if data is enabled
But ur sure it's unlocked? Not sure how the DHD works but I heard that on some G2's when they got them unlocked with a code it wouldn't work anymore (said no service for all sim cards). I doubt it's an issue with the DHD. Have you messaged the unlock company yet? I would . Try this. Oh and toggle wi-fi
Dial *#*#4636#*#*
Sellect phone information and scroll all the way down to the bottom
Select the set preffered network type and change to GSM auto (prl)