Chromium has some issues with its security restrictions when loading stuff from files, in particular when using XmlHttpRequest; Minefield is a little less strict. I suspect you’re hitting that problem.
I don’t know whether this means that Chrome is too paranoid or Minefield too relaxed, but it does mean that if you want to use Chrome for testing your code you’ll need a local web server of some kind. If you’re on Windows, you might want to take a look at Xampl – it’s a lightweight installation of Apache plus related stuff, all nicely packaged for Windows. If you’re on Linux, you probably already have Apache installed. If you’re on the Mac… then I’ve no idea what your options are, but I’m sure you can find something.