finger touch on display screen not working

The other day I went to change the radio station on the display screen and it wouldn't do anything. If i touch around the screen in different places I can change one channel but nothing else. I can't change CDs or even use the touch screen to turn off the display. Can't figure out what's wrong or how to fix. I can change the stations on my steering wheel and do everything I want to on the other buttons everywhere BUT the touch screen. Any ideas?