Ursprünglicher Beitrag von: Avais Gilani ,
If you are using Windows, this is a major problem going around with iTunes right now. The newest update fixes it but requires some effort. You have to uninstall iTunes completely with all other components such as bonjour. After this, go into the system drive and delete all residual data of the iTunes installation. Reinstall ITunes. This should fix the problem. Worked for me.