[boydy]

Ok, without testing MrAd try this,

Template - Header

Add to top:

<!-- Private Message Alert -->
<style type="text/css">
.alert {
    background-color:#F00;
    width:100%;
    height:30px;
    color:#fff;
    font-size:14px;
    display:block;
}
.alert p {
    padding:5px;
}
.alert a {
    color:#ccc;
    text-decoration:none; 
}
</style>
<if condition="$bbuserinfo[pmunread]">
<div class="alert">
<p><span style="text-decoration:blink; font-weight:bold;">ATTENTION! $bbuserinfo[username]</span> You've got $bbuserinfo[pmunread] unread private message(s), click <a href="private.php">here</a> to view.</p></div>
</if>
<!-- Private Message Alert End -->

Should work fine...