[For 1.6] Advanced Sidebox 2.1.1

[.m.]

^ find below code in the above referred latest_threads.php file (lines ~ 209 - 210)

// get forums user cannot view
	$unviewable = get_unviewable_forums(true);

you can follow earlier suggested method

(...) add after above (in a new line) :
$unviewable .= x;
where x is the forum id - which should be excluded. save the file and check if it works as required