I also get unable to retweet, but i get that on twitter.com as well, so im assuming it has nothing to do with the n9? Then again if i look at tweets in my timeline i can see the tweet i tried to retweet from my n9, and it says "undo retweet", which wont undo anything since twitter.com doesnt show me having retweeted it at all. "Undo retweet" turns briefly into "retweet", which when pressed says this: "Your account may not be allowed to perform this action. Please refresh the page and try again." Which doesnt help. So it seems my n9 broke twitter.