The surging popularity of the Twitter messaging service has broken at least one Twitter client application and affected another as a part of what is being called “the Twitpocalypse.”

Each message on Twitter is assigned a unique identification number. On Friday evening, the number of tweets exceeded 2,147,483,6471. While that doesn’t seem like a round number, it’s the largest number that can be stored as the data type known as a “signed integer.” Once that number was exceeded, some versions of some Twitter client apps could break in a fashion similar to what was expected during the Y2K “millennium bug” era.

The first apparent victim of the Twitpocalypse was The Iconfactory’s Twitterrific for iPhone, which stopped working immediately following the event. Though The Iconfactory released a version of the app that the company felt addressed the Twitpocalypse, apparently that assumption was incorrect. Twitterrific users on the iPhone and iPod touch who attempt to contact the service will receive a “YAJL error 3” indication.

A tweet from Twitterrific developer Craig Hockenberry seems to indicate that he’s fixed the bug, but now must wait for Apple to approve the bug-fix release. The Iconfactory has suggested that Twitterrific users follow @twitterrific on Twitter for status updates. Twitterrific users might want to use a free Twitter app such as Twitterfon or Twittelator in the meantime. (Update: Twitterrific's developers report that a fixed version has been submitted to the App Store and awaits Apple's approval. Update x2: Apple rush-approved the bug fix in the free version of Twitterrific late Sunday, with the premium verison still to be approved.)

Atebits Software’s Tweetie has also been affected by the Twitpocalypse. The program continues to function for browsing and posting tweets, but searches no longer work in the Mac version and results appear one at a time in the iPhone version. Tweetie developer Loren Brichter said on Twitter that he is working on an update to address the problem as well. (Update: Brichter posted an update to Tweetie for Mac that addressed the issue on Saturday night.)

If you’re experiencing problems with the Twitter client you use, check to see if you’re using the latest version. Most Twitter clients have already been updated to deal with this issue.

[Updated 10:29 a.m. PT for a correction: it's the Mac version of Tweetie that can't search at all, not the iPhone version. Updated 6:15 p.m. PT with info about Twitterrific update. Updated at 10:16 p.m. with info about Tweetie for Mac update. Updated Sunday 6/14 at 9 p.m. PT with information about release of free Twitterrific with fix.]