I've been getting that buggy app thing too when downloading ANY app, the same error mentioning app x (where x is app name) cannot be downloaded but the current app downloads fine. It's been well over 2 weeks now.Wirelessly posted (iPhone 4s: Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_2_1 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8C148 Safari/6533.18.5)
I don't know what's going on with the iTunes store lately, but it seems really glitchy. For weeks I was getting error messages every time I downloaded an app, saying that another app that never actually downloaded wasn't available. I tried relogging, checking my iTunes/apple ID, and nothing worked until it just decided to DL on its own sweet time.
I've also noticed items I've been billed for and already downloaded don't show as purchased, and I can't write reviews... Meaning to call apple about that now the weekend's over.