I just wrote a blog post about a very similar problem. Probably bug.
I can successfully post on ChainBB forum but the forum are not updating.
The newly posted articles and comments are not visible on the ChainBB forum, only on Steemit. The latest posts on the ChainBB forum are 10 hours old. I think there is a bug or something like that in the forum.
I hope they (the developers) will fix it soon!
Enjoy Steemit! Have a nice day!