[Lynne]

Let me see if I understand what you've done.

You have a site with several forums. One forum, x, you want to have shown with a new template as the first post and the rest of the posts in the thread show the postbit template. For all the other forums, you want the postbit_legacy template to be used.

So, you have postbit_legacy set to be the post template used, then you created a new style, a child of your main one, and replaced the postbit_legacy template with the postbit template. You set this style as the default forum style for that forum in the Forum Manager. And, you have a plugin that says when in forum x, use a new template for the firstpost in the thread.

The way you have done it *should* work. However, there seems to be a problem with another plugin you have that uses the postbit_display_complete hook (executed on line 296 of class_postbit.php as shown in your error.) You may want to try disabling any other product using that hook and see if you get that error.