This is a general post covering all the iTunes problems, i originally posted a problem when trying to add songs to iTunes 11 and seemed to have luck when turning off cloud purchases, there seems to be a problem when using cloud or icloud.
I use iCal and have had no problems until i decided to turn on iCloud, my appointment blocks changed colour and when i turned off iCloud i lost all my appointment blocks and stupidly did not do a backup.
Not sure if this is a coincidence but is as though when cloud purchases or iCloud are off anything you add is added to your harddrive but when cloud purchases or iCloud are on, all the details are stored somewhere out there in the universe.
Just a thought, not a definite solution.
I must add that now i have got to grips with it, iTunes 11 is great to use.