This is a semi-old thread, but I wanted to report to you all what happened to me.

I imported a private key, and as stated in the OP, it showed up in my "Address Book", not my "Receive Coins" list. Well, what I did was shut down the Bitcoin-QT client and re-opened it. When I re-opened it, it told me the wallet was out of sync, and after it finished getting IN sync (hahaha) it showed up in my "Receive Coins" list like I expected it to from the get-go.

I haven't tested sending money to it and sending money out of it, but I'll do that later on when I have enough coins to lost in case something goes wrong.