Just checked my manual, nothing about locking the code out completely.
Each time you enter an incorrect code the time delay doubles before you are able to re-enter the code. Maybe you should disconnect the battery again for 10 mins or so and see if you can put the code in then.
Judging by the book, i would say you need to leave the key in the ignition long enough for 'code' to reappear and then try again. Use the tuning keys (up and down) to enter each digit then press 1 to move on to the next digit.
hope this helps.