Radio only blinks

One night I drove listening to the radio no problem. I stopped off, two hours later returned to my car and the radio was off. I pushed to turn it on and the clock came on for a few seconds and turned back off. Now the clock just continually blinks on and off but will not allow any radio or CD functions. Anyone have any ideas of what this is and how I can fix it? Radio silence is beginning to drive me nuts! Thanks