I'm having this exact same problem!
Tell me if you find something, please!
Maybe some more info could help, this is what I get:
The error happens while creating a new post (or replying or editing), page loads fine (looks fine) but at the state bar in the bottom, there is a message: "Ready but with errors in the page", almost everithing works well in the post form, the post can be made but you can't use BB Code (none of the buttons), smilies, or the preview button, as soon as you try anyone the state bar message changes to: "Error in the page" and nothing happens.
You can see it at my webpage:
http://www.versionti.com/FVM, this is a temporal URL as it is not released yet. The forum is under "Soporte Técnico" Menu and "Foro" stands for Forum in spanish. All my webpage is in spanish including Joomla and Fireboard. if you need a test user try this one:
username: test user
password: testuser
Hope this helps to find out the answer. if there is something else I could try like debugging or logging something, let me know and please, tell me how, as I know almost nothing about web coding.
GReetings!
Jorge Luis