When I connect my iPod to my computer, iTunes display a message, saying that: this computer is no longer allowed to use applications on my iPod. I need to enter my credentials for iTunes Store at each session to be a be to sync my Apps.
- First disconnect your iPod/iPhone.
- Go to C:/programs/iTunes.
- Right click iTunes (Application) > Properties > Compatibility.
- Check "Run this program as administrators".
- Open iTunes and log-in to the Appstore.
- Reconnect your iPod/iPhone and sync your applications ..
Thanks to Mehedad for this tip.