When zooming in or out on Chrome, the widths of elements increases very slightly and causes some elements to shift to the next line.
The actual problem is Chrome adjusts the widths of elements by tenths. So something like 141px will turn into 141.1px which in turn causes all your elements to be just slightly bigger and not fit on one line.
var menuItems = $("#navigation .menu a");
//by just going through the menu items it seems to fix the width rounding on zoom.