Hi Mr. Papa,
Thank you for your thoughts.
It appears that our site has only one other plugin that adds any type of functionality to the default WordPress visual editor is Wishlist Member. Given that Wishlist Member is a very popular and well-used piece of software, as is Simple:Press, I’d expect that if the conflict were between those two, someone would have come across it long ago and a mention of it noted somewhere. So I’m inclined to think that it’s not Wishlist.
As for the theme, we are using the Catalyst framework instead of a pre-canned theme. Even if we disable the Catalyst framework and use the default 2014 theme, we still cannot add a new topic/post if the MCE Editor plugin for S:P is active.
I appreciate your offer of taking a quick peek at my site. It is http://www.alcohemy.com/
The forum is behind a paid Wishlist membership wall, so you won’t be able to see it without a Wishlist account. I would be happy to set you up with a temporary free account so you can see the forum if you’d like. Please let me know.
Many thanks.