My guess is you are receiving an App World update notice for App World itself, as a new version has started hitting devices a few days ago. Check your messages folder to see if there is a message with the App World icon next to it. Click the message and see what happens.
If the message isn't there, then go to BlackBerry - Download BlackBerry App World
and manually download the latest App World to see if that helps. If all else fails, do a battery pull.