Being congested and having a hard time hearing. This seems to be a common thing with me when I get a cold, it's just harder to hear and I hate having to ask for people to repeat things.
But man it would help if they didn't mumble in the first place!! MOVE them lips, folks, they're there for a reason. DH and my oldest seem to be the most guilty of this, and then they get annoyed when they have to repeat themselves. Yes, I know it's no fun to repeat yourself but dangit, if you'd enunciate in the first place, and speak a bit louder, you'd be heard the first time!
Actually DS doesn't get annoyed but DH does. But really man, take the hand away from the mouth at least so I can see if you're lips are moving in a general "yes" direction!