right, but you must use a baud rate of 115200, 9600 won't work I would suspect.
What happens if you use
minicom -b 115200 -o -D /dev/ttyAMA0... I can't explain why you can't reflash though, that should work, unless you use a different baud rate that might not be suitable for the job.
EDIT: at this point it's quite likely your chip is blank with no firmware though, so I guess whether that was the problem initially is a moot point.