Why can't I post replies?

I can't post replies. Whenever I press post, it shows the icon turning but it will return to the word "Post" and has not done anything. Has anyone encountered this problem? I include an attachment as well. I wait for it to finish loading.

Got the same problem, it says "recipient is not your friend" when I try to send a message (even though we are friends) - I unfriended to send another request but now it doesn't let me .-.