On my first attempt at flashing 4977 to a cheapmod via evox, the flash halted about 1/3 of the way through. The clock was still running, so the box had not locked altogether, but the flash never continued. After hot swapping the chip into another box, the 4977 flash went fine. Since then I've done 2 more cheapmod'ed xboxes, and haven't seen the issue again.
I did however chat with another user on IRC who had the same issue I did. Perhaps it's not an altogether isolated incedent?
The-Cableguy