bloginfo returning wrong path (XAMPP on Windows)

I have installed WordPress multi-site on my Win 8 machine using XAMPP 1.8.3. I am working with the PressBooks plugin, which uses a custom theme. I’ve got this plugin working many times before on a hosted server, but am having problems with the local XAMPP install on my machines.

Basically, the stylesheet for the theme is not loading. Here is the code to the stylesheet when I view source:

<link media="screen" href="C:\xampp\htdocs\pressbooks\wp-content\plugins\pressbooks/themes-root/pressbooks-publisher-one/style.css?1380173100" type="text/css" rel="stylesheet">

That path is obviously incorrect. It should begin with http://localhost, not the path to XAMPP htdocs directory.

When I look at the header.php file for the theme, I see that the code to generate the link is:

<link rel="stylesheet" type="text/css" href="<?php bloginfo('stylesheet_url'); echo '?' . filemtime( get_stylesheet_directory() . '/style.css'); ?>" media="screen" />'

So, I test out the bloginfo(‘stylesheet_url’) function and sure enough, it returns the wrong path:

C:\xampp\htdocs\pressbooks\wp-content\plugins\pressbooks/themes-root/pressbooks-publisher-one/style.css

Any idea why this might be? Anyone ever run into this where bloginfo has returned the incorrect path?

Thanks,
Clint