The year of the car would help, but I'll make an assumption based on your description. You might try turning it slower, otherwise it just isn't reading correctly. I've heard those types of units can be sensitive to dust, if the amount allowed to build up in the cabin is excessive, but don't know for sure.

Other than maybe (and this is a total shot in the dark, but easy and worth a try) disconnecting the battery so it resets everything, I don't know... if you do this make sure you have your security code for the radio. I'm assuming you've never removed the knob, I'm not sure if those types can be pulled straight off like the older types. Some can't at least. Just be glad it still works :shrug: