Mmenu doesn't work on IE, please help.

Mmenu doesn't work on IE, please help.

Hello here.

I have no idea why my implementation of mmenu doesn't work on IE (tested on IE 9 and 11):

http://www.virtualsheetmusic.com/zmmenutest.html

Please, resize the window to be 785px width maximum to see the menu (it is a responsive design.)

The menu opens, but the top-fixed bar doesn't move to the right. Also, if you scroll down the page, then you open the menu, the bar gets positioned lower in the page!

It works perfectly on all other modern browsers and mobile.

Any help is very welcome!

Thank you in advance.

Fab.