I have had a few problems with this in the last week or two. If you report them in a forum; they usually have one set up already, they will usually tell you what the problem is and that they are working on it.
I have found that if I am having a problem getting it to post, I can go out of the hub, into my feed and comment on it with no problems. I have done this several times with no problems when I can't get one to post. The share is the same way.