(Image Caption: Twitterrific senses the Twitpocalypse and ceases to function.) Each message on Twitter is assigned a . 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 , 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 for iPhone users attempting to contact the service will receive a “YAJL error 3” indication.

A 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 for status updates. Twitterrific users might want to use a free Twitter app such as or in the meantime.

Atebits Software’s has also been affected by the Twitpocalypse. The program continues to function for browsing and posting tweets, but searches no longer work. Tweetie developer Loren Brichter said on Twitter that as well, but like all iPhone developers he is at the mercy of Apple’s approval process once he’s submitted his fix.

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.