Hello;
don't know what your own template is, but try to change in "top.php":
$main_template = 'top';
by
$templates_used = 'top,whos_online';
$main_template = 'top';
By the way, "whos_online" does not appear in the default "top.html" template page.
Maybe "top.php" is not coded to parse "whos_online"...
I never tried, sorry.