Motorola Droid X :: Ringtone Keeps Changing

I use different ringtones for as many as 12 contacts so that I know who's calling me! Once in a while when the last person that has a dedicated ringtone calls me the default phone ringer set itself to that person's ringtone. I turned off my phone took the battery off and the rebooted, the problem goes away for a awhile and before you know it happens again! It's really bothersome when you think a particular person is calling you, (because of a ringtone) you answer and it someone else.