help with key problem

I have a 97 blazer ls with a strange problem..When i turn the blazer off i cant always get the key out of the ignition.it will turn back to the off position but stays there,wont go back to the removal postion....If i wait for a few minuits or more then turn it forward then back i will hear a click and then it will come out..sometime it works right off others it has to stay in the ignition all day...thank god for keyless entry..