I have been getting that about 40% of the time. After retyping a few replies, I started copying to the clipboard before hitting the "Post" icon. Sometimes it takes 3 tries to get my reply to work.
We've been working to fix these issues and everything looks to now be operating properly. If anyone comes across these issues in the future, please feel free to post here or send an email to [email protected] and we'll look into it as fast as possible.