IIS 7.5 not resolving relative path in JavaScript file

Question

I'm working on a simple JavaScript web app with a file structure of:

index.html
scripts/
  | main.js
styles/
  | main.css
templates/
  | options.mst
  | progress.mst

The JavaScript and CSS files are loading fine, and then I grab the templates with an AJAX call:

_.each(['options', 'progress'], function (templateName) {
  $.ajax({
    url: '../templates/' + templateName + '.mst',
    success: function (data) { templates[templateName] = data },
    error: function () { console.log('Could not load template: ' + templateName); },
  });

This works fine when I serve the site from Python's SimpleHTTPServer, but now that I'm trying to move it to a local IIS 7.5 server it's forming the template URL as though the JavaScript were executing from the root / folder, not /scripts. In other words I'm getting a 404 when it looks for http://localhost/templates/options.mst instead of http://localhost/my-app/templates/options.mst. Does anyone know why this is happening? I've looked at some related posts like this one, but I'd rather not use anything IIS-specific in my code like the ~ operator.

UPDATE: I followed the instructions on this page to enable "parent paths", but I'm still having the same results.