Go into your messaging app settings. Under notifications, double check that it's set to sound only not sound+viberate. If the setting isn't there, check under your sound settings - again, look for notification sounds and check to make sure it's set to sound only, not sound+vibrate. I'm not very familiar with TouchWiz, so I can't tell you exactly where to check. Hopefully this helps. I'm guessing that somewhere/somehow this setting got changed from sound to sound+vibe. I don't think it's a bug or specific to 4.3, but rather a setting that got changed by accident.