ID and password

iMac OS X 10.6.3, Apple TV
Our tv has recently been upgraded to HD so I just re-connected our Apple TV today - it used to work perfectly. The Apple TV icon is not appearing on my iTunes page so, long frustrating story later, I have tried to "update software" thinking this would help solve the problem. I have to enter my Apple ID and password. I have entered the correct information dozens of times and I have been told repeatedly that either the ID or the password are wrong. They are correct! I tried re-setting my password, got the email confirming the change but that doesn't work either. Meanwhile, since my iMac is now asking me to change passwords for internet access and keychain changes I decided to change the password back to the original one. Now when I go to iforgot.apple.com I get the message "an internal server error has occurred". Before I take a sledgehammer to everything, please can someone tell me where I am going wrong?