For some reason, the serial port on the MC9S12DJ256B 80 pin package occasionally shuts down and refuses to respond to input. I fixed the general case, but it still occurs after a power outage. The $#&!(@%& thing is supposed to reset on startup, but occasionally it hangs. I trapped the hang with the debugger, a few times. Twice, I found it pointing to RAM memory, and a third time, it was pointing to the INTERNAL REGISTERS. I set up ENABLE_COP_X at the entry point, but when I checked the associated memory location, it shows this register is disabled, as if it were never set. When it doesn't hang, but operates semi-normally, it occasionally shuts off the serial port. Trapping it with the debugger, makes the problem disappear, without giving a clue what caused the problem in the first place. This is embarassing; it makes us look really bad.