Did this ever get resolved as I have a similar problem?
I am using dropdown menus and a slider. This is working correctly on my PC in Firefox, Chrome, IE11 etc.
However, one user says that in IE11 the dropdown does not appear. I have checked his compatibility view is off (like mine) and if desperate may ask him to reset IE11 to default but would prefer to find out why this happens in case others have a similar problem.
Thanks