You may want to open the message_list.php file and look for a similar code as the one I've posted here.
I had this problem on very narrow themes and simply adjusted this:
<div id="p<?php echo $cur_post['id'] ?>" class="blockpost row_odd firstpost" style="padding-left: 163px;">
As for the inbox/sent block, this I also had to modify adding a new class to the stylesheet. The thing is, is that it looks different in FF and IE so in my case I had to do this:
#messages {
padding: 0px 0px 0px 0px;
margin-top: 66px;
//margin-top: 52px;
}
The id was added around thi sarea as you can see:
require PUN_ROOT.'header.php';
?>
<div class="block2col">
<div class="blockmenu" id="messages">
<h2><span><?php echo $lang_pms['Private Messages'] ?></span></h2>
<div class="box">
<div class="inbox">
<ul>
<li <?php if ($box == 0) echo 'class="isactive"' ?>><a href="message_list.php?box=0"><?php echo $lang_pms['Inbox'] ?></a></li>
<li <?php if ($box == 1) echo 'class="isactive"' ?>><a href="message_list.php?box=1"><?php echo $lang_pms['Outbox'] ?></a></li>
</ul>
</div>
</div>
</div>
Hope this helps.
Bingiman