Just installed this plugin on a fresh WordPress install (3.5.1) using Twenty Twelve theme with no customizations.
Added a test event in a test category and then clicked to view the Add-Ons available and got the following error:
Warning: Invalid argument supplied for foreach() in /home/user/public_html/wp-includes/functions.php on line 2653
Warning: array_unique() [function.array-unique]: The argument should be an array in /home/user/public_html/wp-content/plugins/the-events-calendar/lib/tribe-app-shop.class.php on line 100
No add-ons show.
Wanted to purchase a pro license and use for my clients but this is not a great sign. Anyone have any ideas?