BB code not parsing/rendering
 

When I include bold or italicized words, or other bb code, in a post, the BB code tags appear along with the text.

For example (i added the # on purpose so the example wouldn't bold)

[SIZE=14px][#B]Hello, world[#/B][/SIZE]

What's strange is that on other areas of my forum, such as in the latest activity section, at the very least the bold code seems to be working.

But on the actual post's page itself, the bb code is not parsed.

In the admin backend, when I use the "Test your BB Code" feature, and click "Go", it gives me the following error

Fatal error: Call to undefined method vB_BbCodeParser::handle_bbcode_size() in /home/mywebsite/public_html/forumfolder/core/includes/class_bbcode.php on line 1379

Not sure if that's relevant but thought it might be.

Any help would be great, thank you!