@SuperG: Put the code just above the following in global.php so its run on everypage and you could be able to add the $threadbits variable in any of the templates:
PHP Code:
// parse some global templates
If vB use that variable on any page then you'll need to change this line:
PHP Code:
eval("\$threadbits .= \"".fetch_template('forumhome_latestthreadbit')."\";");
And replace $threadbits with something unique like $my_latest_threads for example and change the variable in the template accordingly.
@M.C. No idea why it should suddenly do that I'm affraid.