Well if the boards look OK, try to get a dfu-util going on the USB port and relfash your OS. If that too does not work, bad P1 modules? (Something i have never had).
You sad that a previous batch (same design) worked alright so no layout changes are likely to blame, how about any build up under the P1? Any chances that a via or solder blob might interfere? It would be strage to see that happen on a whole series of boards though. But if reflash fails, perhaps pull one of the P1s of the board and see whats going on underneath.
Oh, you do have ample power going to the board right?