Event Calendar3 issue

I’ve searched all around for this one, so forgive me if I missed it.

In every theme I have tried, adding the event calendar causes the sidebar to appear on the very bottom of the page in IE. I don’t use IE, but a number of visitors to the website do.

I’ve validated the XHTML
https://validator.w3.org/check?uri=http%3A%2F%2Fwww.omahachurchofchrist.net%2F

All I did was add the following code to the sidebar:

• <h3>Calendar</h3>
  <?php ec3_get_calendar(); ?>
• <h3>Events</h3>
  <?php ec3_get_events(5); ?>

It breaks the Freshy theme, Vermillion Christmas, and everything else except the Default theme.

Any ideas?