WordPress Theme Breaking Plugins like The Event Calendar

I've been working with a wordpress theme from ThemeForest.net and ran into a most peculiar issue. I don't claim to be a WP guru or anything, but the theme stopped working correctly by not showing all the featured articles on the home page. I got an error that looked like this:

Call to a member function get() on a non-object in [website]/wp-includes/query.php on line ##

So that's a bit of a problem. A huge error, right on the home page. No way I can hand this off to the client as a finished site.

It turns out that even though the theme was released recently, it's using some old-style code. Mainly this multiple times in the theme code:

$wp_query = null;

Commenting out the lines where it was setting $wp_query to null, everything started working fantastic.