I have an iPhone 3Gs and os4. I currently have three updates waiting for me in the app store, but every time I try to update them, it takes me to my credit card billing page and asks me to input my security code. I do it and it tells me its invalid (even though it isn't). Not to mention i currently have a remaining balance from a gift card, though I thought updates are free. Please help. I have tried over 3G and wifi, but have not tried it on iTunes yet.