I can't download some of my past purchases
This problem suddenly appeared a while back when synching my iPad. iTunes reported that some of my books couldn't be synched because they couldn't be found. The books have a '!' beside them and seem to have disappeared from my Mac (ie the actual file has disappeared).
Following the instructions I've seen on Apple's support pages I went to the store in iTunes, went to Purchased and the books appear there, but all have a 'downloaded' button greyed out. If I select 'not on this computer' instead of 'All' then the books disappear. I have deleted one of these books from my library to see if I could force iTunes to notice I don't have it currently downloaded, to no avail.
The books appear to still be on the store (I search for them and the price is there for a moment until that changes to 'downloaded' and greys out.
Any ideas?
MacBook Pro with Retina display, OS X Mountain Lion (10.8.4), itunes 11.04