Handset for ATT 5.8 GHz Cordless Telephone Model...

Question

Problem is with the main handset for AT&T 5.8 GHz Cordless Telephone Model 5870 with Talking Caller ID/Call Waiting - about 5 years old.The handset is quite warm to the touch and there is a blue glow around the ear piece which I have never observed before. Otherwise the handset is dead with nothing whatsoever displayed in the viewing window and no dial tone or ability to answer - dead. I replaced the battery according to instructions and waited 24 hours with no change - still dead. Is this handset kaput? Do I just need another one now? WHat would cause this?