Z-Index Issue when viewing photos

My site has a fixed navigation bar including the ES toolbar... when I view a photo posted on the stream the top of the pop-up box appears behind the fixed navigation bar, so I can't get to the options / controls including presumably how to close the pop-up box.

You can see it at: mysite.com/ duathlon - if you click on the photo posted on the stream there.

Can anything be done in the code to ensure the pop-up box always dominates and appears over a fixed nav bar like mine?

Not sure if you can replicate this due to different screen sizes, so attaching a screenshot to help illustrate it.

Thanks!