Steve,
I have since tried another 12F675 and now I'm really baffled!!
I thought MPLAB IDE (release 7.51) was supposed to erase a flash chip! In fact, I checked it afterward and it said "chip is blank". Now, I reprogrammed the other one and it still was flashing gpio.0. The new chip (same hex file) flashes gpio.5! Go figure. I haven't a clue.
Ron