[Snoman002]

Research this some more, try a Google search for Sprint no Caller ID.

I just had a caller ID issue with my phones, and although mine turned out to be a problem on Sprints end there was a thread somewhere that talked about a registry setting that determines how many characters it takes for it to recognize a phone number in the contacts list.

Sorry I cant be of more help, and I dont know why it would all of a suddent start doing this (and a hard reset not fix it) but maybe you can sort it out without taking your phone to the store.