After loading ver 4.2 firmware (don't ask why I loaded 4.2 , was doing some CDMA reprogramming which required older firmware ), the "0" keys, which previously worked, no longer work on 2 separate phones. I've updated back to 4.5 and they still don't work. This is NOT a hardware malfunction, as the phones are new.
You may want to do a complete wipe of the devices with either JL_Cmder or BBSAK and start fresh. I can't tell you why it happened, but I can tell you how to deal with the problem.