AppleTV is no longer recognizing my password.

AppleTV is no longer recognizing my password. I streamed a purchased TV show an hour or so ago and had to enter my password and everything was fine. When I went to stream another episode, I was asked to enter my password and was told it was incorrect. I tried several more times. I verified my password by logging into my iTunes account on my Mac, but AppleTV keeps telling me that it is incorrect. I've had this unit for over 2 years and never had this problem. Unplugging the unit and plugging it back in did not change my circumstances.

Any suggestions?