Did you do a full factory reset within the phone's os? A second important thing, since you mentioned a red x for signal. Is the original Sim card in the phone? Cards for Sim slots in sprint phones are not interchangeable like gsm cards are. The card is paired to the phone from factory. After a full reset, maybe go by a corporate sprint store that has, or can get, a replacement Sim card for your phone. This is the only thing I can think of after all you've said so far. If that doesn't work, then there could be some deep programming involved, ##data#, to get it back into shape. Flashing Roms won't change this deep parameters for a sprint phone. Either will factory resets. You might have got a phone that someone phucked with deeply or you might have bought an expensive paperweight.