My biggest problem with communication is by far that I have nothing to say. Unless I have something concrete to ask or say, I can't come up with anything to say. And after I have said/asked that, I have nothing more to say.
It has always been that way for me. In my 35 years there have only been 3 people I could talk to at length (and not always with any of them), they are/were my mother, my late grandfather and my ex boyfriend. With absolutely everyone else I am only able to answer questions they ask me. I have no idea what to say beyond that.
When I was little, about 5, my mother and I were at a cafeteria with a play area (no such thing now AFAIK, though I could be wrong), and a mother with a girl roughly my age came along. The girl entered the play area where I was, and we started playing and I said something to her. My mother informed me that the girl was deaf. We could just play!
That's not to say that body language and eye contact aren't problematic for me, they are indeed, I can't look anyone in the eye without triggering my fight or flight response, and I have a hard time reading people and being aware of what I emit. But not even being able to come up with anything to say is still a bigger problem.
Anyone seen that scene in Friends where Ross and Mike spend an evening together and have absolutely nothing to say to each other? That's my typical interaction. Not kidding.
I'm not what you'd call sociable but it'd be nice if I had been able to communicate with the few people I come across that I actually take a liking to.