UBB.threads PHP Forum Software Community Forums UBB.threads Version 7/8 Support Error Creating Multiple-Forum RSS Feed

I tried to create a multiple-forum RSS feed by clicking on one of my categories - the Auto category. I set the cache time to 90 minutes, chose recent posts, 0 body and 3 posts. I got the error

Fatal error: Call to a member function convert_time() on a non-object in E:\forums\libs\ubbthreads.inc.php on line 2818