there is definitely one closing div too many before the sidebar call; i suspect this one </div><!-- .entry-content --> in this area:
<div class="photo-column">
<a href="http://www.drchrisstevens.com/blog/?p=7" rel="bookmark"><img src="http://www.drchrisstevens.com/blog/wp-content/uploads/2011/01/jaw-pain.jpg" alt="Post Pic" width="145" height="145"></a>
</div><!-- .entry-content -->
</div>
however, as the page is validating, there must be closing div missing; i suspect : <!-- #wrapper --> in foter.php (the comment is there, but the closing div is not)
a fine example if ‘two wrongs do not make one right’
Wow. I guess the validators don’t see those as well as I thought they would. Thanks very much for seeing that.