Migration to the new data center in NC maybe? Would make sense as to why some people (those connected to the old center still) can still download and to why those who cant (are being routed to the new data center that isn't fully operational yet because of the transition). A wild guess but you never know, they said it would be open spring!
I have three icons - one update, one re-download of Skype that I need right now , and a new purchase - all of them look dark, and have the words 'waiting...' under them all.
You are right, I also got the message that the purchase cannot be done, or - whatever your message was from iTunes - mine was the same.