When you have the caption with button, it sits on top of the image as an invisible layer so the image behind it is only clickable from the very edges where the caption doesn't expand to.
I changed the link on the first image of your homepage to link manually and to use the same link that the image is supposed to go to.
Regarding the 404 error, the link above isn't a 404 error page, that would be this page: http://shop.gobeyondthegrid.com/nonexistant
I'm not sure why the sidebar is getting wrapped incorrectly, but try updating the theme files as its still on 1.0 on your site and there have been some bug fixes with with 1.1, 1.2 and now on 1.3.1 (the update for WooCommerce 2.0).
Most likely in the search.php file, the get_sidebar(); call is mistakenly inside the div for template-search which is causing it to be inside the nine unit grid instead of out of it.
What is should like look like is:
<div class='content template-search <?php avia_layout_class( 'content' ); ?> units'>
/* Run the loop to output the posts.
* If you want to overload this in a child theme then include a file
* called loop-search.php and that will be used instead.
$more = 0;
get_template_part( 'includes/loop', 'search' );
//get the sidebar
$avia_config['currently_viewing'] = 'page';