Unable to Log In APPLE TV

Screeen say on atv that my log in or user name is incorrect and therefore cannot login to Itunes store. My passwords work on the i mac but the same info put in via atv says unable to login. i can listen to internet radio....search i tunes store ie whats new songs video and the like even preview songs and it shows an option to buy. But i cant login to i tunes store from apple tv ,,,,,,,, HELP!!!!! i have the same problem with You Tube as well....i have authorzed and deauthorized and reset my youtube settings so please dont go there