Looks like a problem with your dropdown menu. https://interstateconstructionllc.com/ActiveContentDropDownWide.js
It obviously has some glitches in it when it comes to IE and looks like it is creating a layer over your form that is covering up that field. My guess, however, is that a work around would be to move down the form about 10 pixels and you would be out of the way of the layer that is covering the form.