Specifically, the company writes: "Twitterrific 2.0.1 for the iPhone is indeed experiencing problems with the Twitpocalypse. Investigating now, we apologize for the problems." The Mac version of Twitterrific is unaffected, the company says.
While we've been unable to confirm with the company (update: confirmed via Twitter, updated version expected tomorrow), we've also received numerous reports that Destroy Twitter, a popular desktop application, is affected. We tested the app and were able to confirm that it's attempting to create Tweets with negative IDs in some instances, although we were still able to post to Twitter most of the time.
Some TweetDeck users are also reporting issues with the app continuing to show Tweets that they have already read or deleted. TweetDeck released a patched version earlier today, and those who haven't already are advised to upgrade by clicking the Download button on the TweetDeck website. Not all TweetDeck users are affected.
Other confirmed reports of broken apps include Beak, the new Twitter app for Mac users, which the developer says is being fixed tonight.
All in all, it's a slight inconvenience for Twitter users, but most apps will probably be patched or updated this weekend. It you're experiencing issues with a Twitter app, it's worth checking that you are using the most recent version, and updating if necessary.