Squaregrid fails to render on IE8, wrong html5shiv path when clean_urls are activated.

When using this theme, everything works Ok on browsers that can handle HTML5, but Internet Explorer 8 and lower cannot recognize any of the HTML5 tags (article, aside, footer, etc). So the whole layout breaks, html5shiv is meant to solve that, but even though it is included with the theme, it was not being loaded, because the URL was relative, when you use clean_urls, the site root is given by the global variable $base_path.

Replace this line (31):
$vars['path_to_squaregrid'] = (drupal_get_path('theme', 'squaregrid'));

With this one:
$vars['path_to_squaregrid'] = base_path() . (drupal_get_path('theme', 'squaregrid'));

That will solve the problem. The layout will work on IE8 and IE7 again. I preffer to use the function base_path() for compatibility, so that if the variable someday changes, it will still work.