Recently Jetpack released an update that included a way to make galleries show up as titled layout. It's brilliant really for anyone who works with lots of photos.
However on one of my pages the layout isn't going the full width of the content area: http://www.tophersimon.com/families/family-galleries/
Looking at their support a couple comments said something like:
It’s supposed to fill the entire width, but it defaults to 500px wide if the theme doesn’t define a content width, which it looks like yours doesn’t. You could try adding
if ( ! isset( $content_width ) )
$content_width = 610;
to your theme’s functions.php.
I've tried this but it doesn't seem to make a difference.