I read your post at mybb and the code posted there looks about right.
Replace your postbit template with this and let me know. But before make a bckup of it.
{$ignore_bit}
<a name="pid{$post['pid']}" id="pid{$post['pid']}"></a>
<table border="0" cellspacing="{$theme['borderwidth']}" cellpadding="{$theme['tablespace']}" class="tborder" style="{$post_extra_style} {$post_visibility}" id="post_{$post['pid']}">
<tbody>
<tr>
<td class="tcat">
<div class="float_left smalltext">
{$post['postdate']}, {$post['posttime']} <span id="edited_by_{$post['pid']}">{$post['editedmsg']}</span>
</div>
{$post['posturl']}
</td>
</tr>
<tr>
<td class="trow1 {$unapproved_shade}">
<table cellspacing="0" cellpadding="0" border="0" style="width: 100%;">
<tr>
<td class="post_avatar" width="1" style="{$post['avatar_padding']}">
{$post['useravatar']}
</td>
<td class="post_author">
<strong><span class="largetext"><a href="#"
id="profilelink_{$post['pid']}">{$post['username_formatted']}</span></strong></a>
<div id="profilelink_{$post['pid']}_popup" class="popup_menu" style="display: none;">
<div class="popup_item_container">
<a
href="{$mybb->settings['bburl']}/member.php?action=profile&uid={$post['uid']}"
class="popup_item">view Profile</a>
</div>
<div class="popup_item_container">
<a
href="{$mybb->settings['bburl']}/search.php?action=finduser&uid={$post['uid']}"
class="popup_item">find Users Posts</a>
</div>
<div class="popup_item_container">
<a
href="{$mybb->settings['bburl']}/search.php?action=finduserthreads&uid={$post['uid']}"
class="popup_item">find Users Threads</a>
</div>
<div class="popup_item_container">
<a href="{$post['website']}" target="_blank" " class="popup_item">visit Users Website</a>
</div>
<div class="popup_item_container">
<a
href="{$mybb->settings['bburl']}/private.php?action=send&uid={$post['uid']}"
class="popup_item">PM User</a>
</div>
<div class="popup_item_container">
<a
href="{$mybb->settings['bburl']}/member.php?action=emailuser&uid={$post['uid']}"
class="popup_item">E-Mail User</a>
</div>
</div><br />
<script language="javascript" type="text/javascript">
new PopupMenu("profilelink_{$post['pid']}");
</script> {$post['onlinestatus']}<br />
<span class="smalltext">
{$post['usertitle']}<br />
{$post['userstars']}
{$post['groupimage']}
</span>
</td>
<td class="smalltext post_author_info" width="165">
{$post['user_details']}
</td>
</td>
</tr>
</table>
</td>
</tr>
<tr>
<td class="trow2 post_content {$unapproved_shade}">
<span class="smalltext"><strong>{$post['icon']}{$post['subject']} {$post['subject_extra']}</strong></span>
<div class="post_body" id="pid_{$post['pid']}">
{$post['message']}
</div>
{$post['attachments']}
{$post['signature']}
<div class="post_meta" id="post_meta_{$post['pid']}">
{$post['iplogged']}
</div>
</td>
</tr>
<tr>
<td class="trow1 post_buttons {$unapproved_shade}">
<div class="author_buttons float_left">
{$post['button_email']}{$post['button_pm']}{$post['button_www']}{$post['button_find']}
</div>
<div class="post_management_buttons float_right">{$post['button_edit']}{$post['button_quickdelete']}{$post['button_quote']}{$post['button_multiquote']}{$post['button_report']}{$post['button_warn']}{$post['button_reply_pm']}{$post['button_replyall_pm']}{$post['button_forward_pm']}{$post['button_delete_pm']}
</div>
</td>
</tr>
</tbody>
</table>
This is very easy, basically wrapping up with a div the popup_item_container class each of the links that you want to make appear as drop downs. Let me know how it will go.