Drop Down Menu appearing beneath WordPress content in IE

Currently wrapping up a site for a new granola product and my problem is the CSS drop down menu is appearing behind the WordPress content area in IE. At least Internet Explorer 7. Works fine in Firefox and Safari. Here’s an example page:

https://www.granolagourmet.com/amazing-things-happen-when-you-least-expect-them-to/

and in case you’re wondering, it’s not happening in the store which is a ZenCart template.

https://www.granolagourmet.com/store/

So it’s a WordPress thing. But why?