This occurs in Windows 7 64-bit. The solution is what Katrina S. suggests. ”
Make sure your windows permissions are correct.
Go into Windows Explorer. Find this folder
C:users username My MusiciTunes
Right-click > Properties, and go to the Security tab. Make sure your userID has full control and ownershipover that entire itunes folder, and all its /child/subfolders.
You’ll have to restart itunes so it will read the new permission settings.
This link has some screenshots of what I’m talking about.