Twitterrific is No Longer Autoupdating/Growl Has Stopped Showing Mentions (Mac)

Why isn't Twitterrific autoupdating anymore? Why has Growl stopped showing my mentions?

If your autoupdate and/or Growl settings are properly set and you're still having problems, it could be becasue you closed your timeline window in Twitterrific. Instead of closing the window by clicking on the red "close" button in the upper-left corner (or by pressing ⌘W), hide Twitterrific by pressing ⌘H. This keeps your timeline active and allows it to continue to automatically update.