If there were no updates to Carbonite (recently), and you didn't recently install any other addons, then I would say that you should restart your World of Warcraft game (completely exit the game back to your desktop and then you can restart it
).
If you HAVE installed an addon, you can try to disable that addon and see if the error stops. If it does, then there is obviously an interference issue with that addon and Carbonite (but, it might be interfering with another addon and the game is just spitting out an error that blames Carbonite).