Last night the owners of iDevices started to complain about the fact that the iTunes App Store works intermittently and downloading an application is almost impossible. Apple works on both the iOS App Store and the Mac App Store, so it is very possible that you have problems with both now. The above error was displayed to me this morning when I tried to open the iTunes App Store and unfortunately it appears on the screens of many users since last evening, but Apple is more than likely working on solving the problems.
I don't know how long it will take until the App Store returns to normal, but it's been hours since the store has been down, so everything will probably be resolved in the next few hours.
