I got my iPad yesterday, and a few times I switched between the US and UK iTunes stores. After I synced the iPad it always changed over to the respective store, so when it was US I could download iBooks and buy US apps etc. But last night, and today, it won't seem to let me switch back to US iTunes. If I log in to the US iTunes on my PC then sync, I still get the message on my iPad that I can't access the app store (this happens on iBooks store too). Have I changed a setting somewhere, or done something to make it stop working? Any advice would be gratefully appreciated!