When I downloaded the Itunes update (7.6) I installed it, and now I can't use the store. I get a message something like Itunes cannot connect to store, as it was unable to establish a connection to a network. I have been told it might be something to do with norton protection center / norton antivirus, but I am not sure what settings I have to change.

I went through the same issues you did. Itunes would work fine but when i wanted to connect to the store it would start to work but then say the same thing. All i wanted to do was to create an itunes account to get album artwork but i could never connect. What i did to get it to work was simply borrowed an ipod from my sister and then plugged it in...go figure it worked fine when i purchased the product. Idk why it worked when i did this but it did and i only had to do it once. But a friend of mine had the same issue and simply disabled his antivirus and presto it worked like a charm so either of those would work for you hopefully...good luck