The SPC on all VZW phones is always 000000 unless changed by the user.
It has to be to accept the OTA service programming when doing *228.
I just tested it on my rooted D2G for argument's sake and it works fine.
If it has been changed on your phone and you don't know what it is then you will have to read the NVM with RadioComm to get the code and then reset it to 000000.
Flashing an SBF would also reset the SPC to 000000 but it hasn't been released publicly yet so RadioComm is your only option at present.
You will need a recent version 11.11.7 or later to have support for the MDM6600 chipset that can read the D2G.
I don't think I am allowed to post any further links or info on this forum, unfortunately.
I am at work but may have anther solution. Try using AnyCut from the market to set a shortcut to Programming menu from activities. Then open the programming menu and select user activation. It should let you into that menu without the SPC. If not I can help you later tonight with radiocomm.
the SPC code '000000' works only if you are in CDMA mode. In GSM/UMTS mode code is not 000000. I can confirm that.