If you enter a code in wrong you could have permanently locked the radio. You usually get 5 to 10 attempts before it locks out. Some radio's just lock out for a certain amount of time, others require re-programming at a radio repair centre (or your local radio decoding place).
Leave the radio powered up in the locked state and do not press any buttons. It could take upto 24 hours. If you have managed to get it in this state then you must have entered the code in wrong a number of times and the code you have must be wrong anyway and I would advise taking it to your local radio decoding specialist.
Dave
April 2006