Menu bar on web site fails on Internet Explorer

A user reports:

I was checking out the lessons, and when you do the top menu bar stops functioning completely. You cannot select anything to see sub folders and whatnot. I have attached a screenshot.
I am using the latest version of internet explorer to view the site.

See @gvwilson for user's contact info.

![site bug](https://f.cloud.github.com/assets/911566/146204/da13f520-7480-11e2-8617-7fed631bc974.png)