I cant update anything on app store?!?

Ok, i have a 4g Ipod touch. I check my updates for the App Store daily. I noticed i had 2 apps needed to be updated: Facebook and Carnivores. I clicked update, and it said "Invalid adress. Sign in" So i signed it. It came up with the page that asks name, address, etc. Same thing as when you first sign up for itunes on the Ipod touch. anyway, after that, it didnt update. So i pushed update again, and the same thing popped up. Same steps. It wont let me update anything now. Its a never ending cycle! Please help!!!