Funny you should ask this. I just found a great piece of writing on this very topic.
My problems tend to be due to things like getting nervous and talking faster or softer, because I'm afraid of what they might think of my words or answer, which invariably leads to mumbling of some form. I also sometimes stutter a bit; especially on the first word or a word that just doesn't want to be spoken at that particular moment. Then, I also have the mental block bit. I know how to speak, and I have words to use, but sometimes, all that will come through is sensory info, like the smell of the subject or the color of the word, which needless to say, helps nada. Or I'll forget what it is that I'm saying. Or I'll be distracted and end up on an entirely unrelated subject. Or I'll end up on a seemingly entirely other subject that is based on a logical leap to me, but hard to explain to others.
_________________
"I am to misbehave" - Mal
BATMAN: I'll do everything I can to rehabilitate you.
CATWOMAN: Marry me.
BATMAN: Everything except that.
http://lastcrazyhorn.wordpress.com - "Odd One Out: Reality with a refreshing slice of aspie"