Hmm.... I tested the snipped posted, in FF and IE - both worked fine.
So I have no clue why it's so off for you.
But you can try to put the shoutbox and the WOL inside a table, as a workaround.
To do this, replace the snippet post by this one:
Code:
<table width="100%"><tr><td width="88%">
<div id="vbshout" style="overflow:auto;height:{$vboptions['shout_box_height']}px;width:100%;float:left;">
Loading...
</div>
</td><td width="12%">
<div id="vbshoutwol" class="alt2" style="overflow:auto;height:{$vboptions['shout_box_height']}px;width:100%;float:right;">
<div id="vbshoutwolhd" class="tcat">Shouting:</div>
<div id="vbshoutwolusers">
Loading...
</div>
</div>
</td></tr></table>
This puts it into a table with one row for the shoutbox itself and one for the WOL.