Have you put in the closing tags etc?
Code:
if condition="$show['loggedinusers']">
<!-- logged-in users -->
<table class="tborder" cellpadding="$stylevar[cellpadding]" cellspacing="$stylevar[cellspacing]" border="0" width="100%" align="center">
<thead>
<tr>
<td class="tcat" colspan="2">$vbphrase[currently_active_users]</td>
</tr>
</thead>
<tbody>
<tr>
<td class="thead" colspan="2">
$totalonline (<phrase 1="$numberregistered" 2="$numberguest">$vbphrase[x_members_and_y_guests]</phrase>)
</td>
</tr>
</tbody>
<tbody id="collapseobj_forumhome_activeusers" style="$vbcollapse[collapseobj_forumhome_activeusers]">
<tr>
<td class="alt2"><a href="online.php$session[sessionurl_q]" rel="nofollow"><img src="$stylevar[imgdir_misc]/whos_online.gif" alt="$vbphrase[view_whos_online]" border="0" /></a></td>
<td class="alt1" width="100%">
<div class="smallfont">
<div style="white-space: nowrap"><phrase 1="$recordusers" 2="$recorddate" 3="$recordtime">$vbphrase[most_users_ever_online_was_x_y_at_z]</phrase></div>
<div>$activeusers</div>
</div>
</td>
</tr>
</tbody>
</table>
<!-- end logged-in users -->
</if>
<br />