This sounds like the famous Uverse issue. Try using the DNS from google. These are at
Lookup google DNS for more details.
I have a SamsungHT-D6750Series_ZA. We recently moved and had to change internet providers. Even though it says we are connected to the internet, Smart Hub shows to be constantly downloading and installing. Howerever, it just loops right back to the menu screen. Does anybody have any suggestions?